build: actually run import-patches on gclient sync (#17885)

script/git-import-patches

@@ -17,13 +17,7 @@ def main(argv):
       help="use 3-way merge to resolve conflicts")
   args = parser.parse_args(argv)
 
-  # save the upstream HEAD so we can refer to it when we later export patches
-  git.update_ref(
-      repo='.',
-      ref='refs/patches/upstream-head',
-      newvalue='HEAD'
-  )
-  git.am(
+  git.import_patches(
       repo='.',
       patch_data=patch_from_dir(args.patch_dir),
       threeway=args.threeway