[bot_update] Remove "git retry" call.

The Git wrapper now implicitly retries, so this call is unnecessary.

BUG=chromium:721450
TEST=None
R=hinoka@chromium.org, iannucci@chromium.org

Change-Id: I79e42aa050f6fec14506b685d379a76e8296fea3
Reviewed-on: https://chromium-review.googlesource.com/506493Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Daniel Jacques <dnj@chromium.org>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -661,7 +661,7 @@ def apply_gerrit_ref(gerrit_repo, gerrit_ref, root, gerrit_reset,
   # command will do so. See http://crbug.com/692067.
   git('reset', '--hard', cwd=root)
   try:
-    git('retry', 'fetch', gerrit_repo, gerrit_ref, cwd=root, tries=1)
+    git('fetch', gerrit_repo, gerrit_ref, cwd=root, tries=1)
     git('checkout', 'FETCH_HEAD', cwd=root)
 
     if gerrit_rebase_patch_ref: