Fix GcsEndpoint serialization in GcsOptions (#36879)

Author: liferoad

sdks/java/extensions/google-cloud-platform-core/src/main/java/org/apache/beam/sdk/extensions/gcp/options/GcsOptions.java

@@ -76,7 +76,6 @@ public interface GcsOptions extends ApplicationNameOptions, GcpOptions, Pipeline
   void setExecutorService(ExecutorService value);
 
   /** GCS endpoint to use. If unspecified, uses the default endpoint. */
-  @JsonIgnore
   @Hidden
   @Description("The URL for the GCS API.")
   String getGcsEndpoint();