git_cache: don't lose options in upload_bootstrap.

I noticed that chromium/src archive grew 2x from 7.3GiB in August
to 15+ GiB now. Turns out --aggressive-gc had no effect.

R=iannucci

Change-Id: I6a27f67f5a4dd2101ac1622221106e094af4688a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1928583
Auto-Submit: Andrii Shyshkalov <tandrii@google.com>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>

git_cache.py

@@ -733,8 +733,8 @@ def CMDupdate_bootstrap(parser, args):
     print('Skipped populate step.')
 
   # Get the repo directory.
-  options, args = parser.parse_args(args)
-  url = args[0]
+  _, args2 = parser.parse_args(args)
+  url = args2[0]
   mirror = Mirror(url)
   mirror.update_bootstrap(options.prune, options.gc_aggressive)
   return 0