Removed python test from protobuf_at_head test

tools/internal_ci/linux/grpc_build_submodule_at_head.sh

@@ -51,6 +51,8 @@ case "$SUBMODULE_NAME" in
     ;;
   protobuf)
     BAZEL_DEP_NAME="com_google_protobuf"
+    # TODO(xuanwang-amos): Remove the following once python test gets fixed for protobuf-at-head test.
+    EXTRA_EXCLUDE_FILTER="python"
     ;;
 esac
 if [ -z "$BAZEL_DEP_NAME" ]
@@ -88,4 +90,4 @@ tools/buildgen/generate_projects.sh
 git add -A
 git -c user.name='foo' -c user.email='foo@google.com' commit -m 'Update submodule' --allow-empty
 
-tools/run_tests/run_tests_matrix.py -f linux --exclude c sanity basictests_arm64 openssl dbg --inner_jobs 16 -j 2 --internal_ci --build_only
+tools/run_tests/run_tests_matrix.py -f linux --exclude c sanity basictests_arm64 openssl dbg $EXTRA_EXCLUDE_FILTER --inner_jobs 16 -j 2 --internal_ci --build_only