fix: revert generics syntax change in MockHttpService test utility (#1574)

* fix: revert generic change in method signature of MockHttpService

Author: chanseokoh

gax-httpjson/src/main/java/com/google/api/gax/httpjson/longrunning/stub/HttpJsonOperationsStub.java

@@ -297,8 +297,8 @@ protected HttpJsonOperationsStub(
   }
 
   @InternalApi
-  public static List<ApiMethodDescriptor<?, ?>> getMethodDescriptors() {
-    List<ApiMethodDescriptor<?, ?>> methodDescriptors = new ArrayList<>();
+  public static List<ApiMethodDescriptor> getMethodDescriptors() {
+    List<ApiMethodDescriptor> methodDescriptors = new ArrayList<>();
     methodDescriptors.add(listOperationsMethodDescriptor);
     methodDescriptors.add(getOperationMethodDescriptor);
     methodDescriptors.add(deleteOperationMethodDescriptor);

gax-httpjson/src/test/java/com/google/api/gax/httpjson/MockHttpServiceTest.java

@@ -143,7 +143,7 @@ public PathTemplate getPathTemplate() {
           .setResponseParser(PET_RESPONSE_PARSER)
           .build();
 
-  private static final List<ApiMethodDescriptor<?, ?>> SERVER_METHOD_DESCRIPTORS =
+  private static final List<ApiMethodDescriptor> SERVER_METHOD_DESCRIPTORS =
       Lists.newArrayList(methodDescriptor);
 
   private static MockHttpService testService =

gax-httpjson/src/test/java/com/google/api/gax/httpjson/testing/MockHttpService.java

@@ -55,7 +55,7 @@ public final class MockHttpService extends MockHttpTransport {
   private final Multimap<String, String> requestHeaders = LinkedListMultimap.create();
   private final List<String> requestPaths = new LinkedList<>();
   private final Queue<HttpResponseFactory> responseHandlers = new LinkedList<>();
-  private List<ApiMethodDescriptor<?, ?>> serviceMethodDescriptors;
+  private List<ApiMethodDescriptor> serviceMethodDescriptors;
   private String endpoint;
 
   /**
@@ -66,8 +66,7 @@ public final class MockHttpService extends MockHttpTransport {
    * @param pathPrefix - the fixed portion of the endpoint URL that prefixes the methods' path
    *     template substring.
    */
-  public MockHttpService(
-      List<ApiMethodDescriptor<?, ?>> serviceMethodDescriptors, String pathPrefix) {
+  public MockHttpService(List<ApiMethodDescriptor> serviceMethodDescriptors, String pathPrefix) {
     this.serviceMethodDescriptors = ImmutableList.copyOf(serviceMethodDescriptors);
     endpoint = pathPrefix;
   }