bevy_pbr: Normalize skinned normals

This was forgotten in bevyengine#5666 when normalization of normals was moved from the
fragment to vertex stage.

crates/bevy_pbr/src/render/skinning.wgsl

@@ -30,9 +30,13 @@ fn skin_normals(
     model: mat4x4<f32>,
     normal: vec3<f32>,
 ) -> vec3<f32> {
-    return inverse_transpose_3x3(mat3x3<f32>(
-        model[0].xyz,
-        model[1].xyz,
-        model[2].xyz
-    )) * normal;
+    return normalize(
+        inverse_transpose_3x3(
+            mat3x3<f32>(
+                model[0].xyz,
+                model[1].xyz,
+                model[2].xyz
+            )
+        ) * normal
+    );
 }