Remove unused header in process_group_agent.h (#35767)

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/35767

Test Plan: Imported from OSS

Differential Revision: D20771900

Pulled By: mrshenli

fbshipit-source-id: af88abfabfbe3d2d94407942738f7dcdfc3f30e2
diff --git a/torch/csrc/distributed/rpc/process_group_agent.h b/torch/csrc/distributed/rpc/process_group_agent.h
index 3175ed7..0bcb171 100644
--- a/torch/csrc/distributed/rpc/process_group_agent.h
+++ b/torch/csrc/distributed/rpc/process_group_agent.h
@@ -2,7 +2,6 @@
 
 #include <c10/core/thread_pool.h>
 #include <c10d/ProcessGroup.hpp>
-#include <torch/csrc/distributed/rpc/python_rpc_handler.h>
 #include <torch/csrc/distributed/rpc/rpc_agent.h>
 
 #include <atomic>