reverted change on thread manager test

test/cpp/thread_manager/thread_manager_test.cc

@@ -21,12 +21,13 @@
 #include <memory>
 #include <string>
 
+#include <gflags/gflags.h>
 #include <grpc/support/log.h>
 #include <grpc/support/port_platform.h>
 #include <grpcpp/grpcpp.h>
 
-#include "test/cpp/util/test_config.h"
 #include "src/cpp/thread_manager/thread_manager.h"
+#include "test/cpp/util/test_config.h"
 
 namespace grpc {