[upstream_utils] Clean up package imports (#6857)

upstream_utils/stack_walker.py

@@ -4,14 +4,7 @@ import os
 import shutil
 import subprocess
 
-from upstream_utils import (
-    get_repo_root,
-    clone_repo,
-    comment_out_invalid_includes,
-    walk_cwd_and_copy_if,
-    git_am,
-    Lib,
-)
+from upstream_utils import Lib
 
 
 def crlf_to_lf():