Remove gerrit_rebase_patch_ref flag from bot_update API
Remove gerrit_rebase_patch_ref flag from bot_update API

BUG=612417

Review-Url: https://codereview.chromium.org/2317213002

primiano/depot_tools,CoherentLabs/depot_tools,CoherentLabs/depot_tools,primiano/depot_tools,primiano/depot_tools