Remove MONO ifdef from Vector128 bitcasts

Follow-up to dotnet#104309.

Author: xtqqczze

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs

@@ -106,11 +106,7 @@ public static Vector128<TTo> As<TFrom, TTo>(this Vector128<TFrom> vector)
             ThrowHelper.ThrowForUnsupportedIntrinsicsVector128BaseType<TFrom>();
             ThrowHelper.ThrowForUnsupportedIntrinsicsVector128BaseType<TTo>();
 
-#if MONO
-            return Unsafe.As<Vector128<TFrom>, Vector128<TTo>>(ref vector);
-#else
             return Unsafe.BitCast<Vector128<TFrom>, Vector128<TTo>>(vector);
-#endif
         }
 
         /// <summary>Reinterprets a <see cref="Vector128{T}" /> as a new <see cref="Vector128{Byte}" />.</summary>
@@ -174,27 +170,13 @@ public static Vector128<TTo> As<TFrom, TTo>(this Vector128<TFrom> vector)
         /// <param name="value">The vector to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Plane" />.</returns>
         [Intrinsic]
-        internal static Plane AsPlane(this Vector128<float> value)
-        {
-#if MONO
-            return Unsafe.As<Vector128<float>, Plane>(ref value);
-#else
-            return Unsafe.BitCast<Vector128<float>, Plane>(value);
-#endif
-        }
+        internal static Plane AsPlane(this Vector128<float> value) => Unsafe.BitCast<Vector128<float>, Plane>(value);
 
         /// <summary>Reinterprets a <see cref="Vector128{Single}" /> as a new <see cref="Quaternion" />.</summary>
         /// <param name="value">The vector to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Quaternion" />.</returns>
         [Intrinsic]
-        internal static Quaternion AsQuaternion(this Vector128<float> value)
-        {
-#if MONO
-            return Unsafe.As<Vector128<float>, Quaternion>(ref value);
-#else
-            return Unsafe.BitCast<Vector128<float>, Quaternion>(value);
-#endif
-        }
+        internal static Quaternion AsQuaternion(this Vector128<float> value) => Unsafe.BitCast<Vector128<float>, Quaternion>(value);
 
         /// <summary>Reinterprets a <see cref="Vector128{T}" /> as a new <see cref="Vector128{SByte}" />.</summary>
         /// <typeparam name="T">The type of the elements in the vector.</typeparam>
@@ -244,27 +226,13 @@ internal static Quaternion AsQuaternion(this Vector128<float> value)
         /// <param name="value">The plane to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Vector128{Single}" />.</returns>
         [Intrinsic]
-        internal static Vector128<float> AsVector128(this Plane value)
-        {
-#if MONO
-            return Unsafe.As<Plane, Vector128<float>>(ref value);
-#else
-            return Unsafe.BitCast<Plane, Vector128<float>>(value);
-#endif
-        }
+        internal static Vector128<float> AsVector128(this Plane value) => Unsafe.BitCast<Plane, Vector128<float>>(value);
 
         /// <summary>Reinterprets a <see cref="Quaternion" /> as a new <see cref="Vector128{Single}" />.</summary>
         /// <param name="value">The quaternion to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Vector128{Single}" />.</returns>
         [Intrinsic]
-        internal static Vector128<float> AsVector128(this Quaternion value)
-        {
-#if MONO
-            return Unsafe.As<Quaternion, Vector128<float>>(ref value);
-#else
-            return Unsafe.BitCast<Quaternion, Vector128<float>>(value);
-#endif
-        }
+        internal static Vector128<float> AsVector128(this Quaternion value) => Unsafe.BitCast<Quaternion, Vector128<float>>(value);
 
         /// <summary>Reinterprets a <see cref="Vector2" /> as a new <see cref="Vector128{Single}" /> with the new elements zeroed.</summary>
         /// <param name="value">The vector to reinterpret.</param>
@@ -282,14 +250,7 @@ internal static Vector128<float> AsVector128(this Quaternion value)
         /// <param name="value">The vector to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Vector128{Single}" />.</returns>
         [Intrinsic]
-        public static Vector128<float> AsVector128(this Vector4 value)
-        {
-#if MONO
-            return Unsafe.As<Vector4, Vector128<float>>(ref value);
-#else
-            return Unsafe.BitCast<Vector4, Vector128<float>>(value);
-#endif
-        }
+        public static Vector128<float> AsVector128(this Vector4 value) => Unsafe.BitCast<Vector4, Vector128<float>>(value);
 
         /// <summary>Reinterprets a <see cref="Vector{T}" /> as a new <see cref="Vector128{T}" />.</summary>
         /// <typeparam name="T">The type of the elements in the vector.</typeparam>
@@ -361,14 +322,7 @@ public static Vector3 AsVector3(this Vector128<float> value)
         /// <param name="value">The vector to reinterpret.</param>
         /// <returns><paramref name="value" /> reinterpreted as a new <see cref="Vector4" />.</returns>
         [Intrinsic]
-        public static Vector4 AsVector4(this Vector128<float> value)
-        {
-#if MONO
-            return Unsafe.As<Vector128<float>, Vector4>(ref value);
-#else
-            return Unsafe.BitCast<Vector128<float>, Vector4>(value);
-#endif
-        }
+        public static Vector4 AsVector4(this Vector128<float> value) => Unsafe.BitCast<Vector128<float>, Vector4>(value);
 
         /// <summary>Reinterprets a <see cref="Vector128{T}" /> as a new <see cref="Vector{T}" />.</summary>
         /// <typeparam name="T">The type of the elements in the vector.</typeparam>