chore: removes 32 API surface after migration

Co-authored-by: Vincent Biret <vincentbiret@hotmail.com>

Author: baywet

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

@@ -176,12 +176,6 @@ public override void SerializeAsV31(IOpenApiWriter writer)
             SerializeAsWithoutLoops(writer, (w, element) => (element is IOpenApiSchema s ? CopyReferenceAsTargetElementWithOverrides(s) : element).SerializeAsV31(w));
         }
 
-        /// <inheritdoc/>
-        public override void SerializeAsV32(IOpenApiWriter writer)
-        {
-            SerializeAsWithoutLoops(writer, (w, element) => (element is IOpenApiSchema s ? CopyReferenceAsTargetElementWithOverrides(s) : element).SerializeAsV32(w));
-        }
-
         /// <inheritdoc/>
         public override void SerializeAsV3(IOpenApiWriter writer)
         {

src/Microsoft.OpenApi/PublicAPI.Unshipped.txt

@@ -2,4 +2,3 @@
 Microsoft.OpenApi.JsonSchemaReference.Extensions.get -> System.Collections.Generic.IDictionary<string!, Microsoft.OpenApi.IOpenApiExtension!>?
 Microsoft.OpenApi.JsonSchemaReference.Extensions.set -> void
 Microsoft.OpenApi.OpenApiSchemaReference.Extensions.set -> void
-override Microsoft.OpenApi.OpenApiSchemaReference.SerializeAsV32(Microsoft.OpenApi.IOpenApiWriter! writer) -> void