fix(#20201): static access to normalizeMediaType in typescript object serializer (#20202)

accessing `normalizeMediaType` should be done static in `ObjectSerializer`, as described
in #20201.

fix applies only to the `typescript` generator.

Author: bbortt

modules/openapi-generator/src/main/resources/typescript/model/ObjectSerializer.mustache

@@ -287,7 +287,7 @@ export class ObjectSerializer {
             return "application/json";
         }
 
-        const normalMediaTypes = mediaTypes.map(this.normalizeMediaType);
+        const normalMediaTypes = mediaTypes.map(ObjectSerializer.normalizeMediaType);
 
         for (const predicate of supportedMimeTypePredicatesWithPriority) {
             for (const mediaType of normalMediaTypes) {