fix: aligns callback parameter name with interface

Signed-off-by: Vincent Biret <vibiret@microsoft.com>

Author: baywet

src/Microsoft.OpenApi/Models/References/OpenApiCallbackReference.cs

@@ -117,11 +117,11 @@ public void SerializeAsV31(IOpenApiWriter writer)
         }
 
         /// <inheritdoc/>
-        public IOpenApiCallback CopyReferenceAsTargetElementWithOverrides(IOpenApiCallback openApiExample)
+        public IOpenApiCallback CopyReferenceAsTargetElementWithOverrides(IOpenApiCallback source)
         {
             // the copy here is never called since callbacks do not have any overridable fields.
             // if the spec evolves to include overridable fields for callbacks, the serialize methods will need to call this copy method.
-            return openApiExample is OpenApiCallback ? new OpenApiCallback(this) : openApiExample;
+            return source is OpenApiCallback ? new OpenApiCallback(this) : source;
         }
 
         /// <inheritdoc/>