add missing generated files
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index 19b4a9b..cb0a3e5 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -810,6 +810,7 @@
include/grpc++/impl/codegen/completion_queue.h \
include/grpc++/impl/codegen/completion_queue_tag.h \
include/grpc++/impl/codegen/config.h \
+include/grpc++/impl/codegen/config_protobuf.h \
include/grpc++/impl/codegen/core_codegen.h \
include/grpc++/impl/codegen/core_codegen.h \
include/grpc++/impl/codegen/core_codegen_interface.h \
@@ -817,6 +818,7 @@
include/grpc++/impl/codegen/grpc_library.h \
include/grpc++/impl/codegen/metadata_map.h \
include/grpc++/impl/codegen/method_handler_impl.h \
+include/grpc++/impl/codegen/proto_utils.h \
include/grpc++/impl/codegen/rpc_method.h \
include/grpc++/impl/codegen/rpc_service_method.h \
include/grpc++/impl/codegen/security/auth_context.h \