[Vulnerability] Fix b/265200538

Change-Id: I1b5e784bd9f0002f858d2a432d9b8453ed212683
diff --git a/rpc_tool/verify_rpc.sh b/rpc_tool/verify_rpc.sh
index c77f4d0..c0e2a21 100644
--- a/rpc_tool/verify_rpc.sh
+++ b/rpc_tool/verify_rpc.sh
@@ -23,7 +23,6 @@
 {
   python3 -m venv $HOME/$RPC_VENV
   source $HOME/$RPC_VENV/bin/activate
-  python -m pip install --upgrade pip
   pip install --require-hashes -r $BASEDIR/verify_rpc/requirements.txt
   export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python
 }