[bot_update] Pass git_repo param in test

Pass git_repo param when calling buildbucket.test_api.try_build.

TBR=hinoka@chromium.org
Change-Id: Ic4a3d270ef3477cb21e4e02d8a22caf7996757b3
Reviewed-on: https://chromium-review.googlesource.com/1213555
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Commit-Queue: Nodir Turakulov <nodir@chromium.org>

recipes/recipe_modules/bot_update/examples/buildbucket.py

@@ -44,4 +44,4 @@ def GenTests(api):
 
   yield api.test('try') + api.buildbucket.try_build(
       'v8', 'try', 'builder',
-      gerrit_host='chromium-review.googlesource.com')
+      git_repo='https://chromium.googlesource.com/v8/v8')