[release] Remove unused sheriff feature from auto-roller.

tools/release/auto_roll.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import json
 import os
 import sys
 import urllib
@@ skipping 47 matching lines @@
   def RunStep(self):
     if self._options.roll:
       args = [
         "--author", self._options.author,
         "--reviewer", self._options.reviewer,
         "--chromium", self._options.chromium,
         "--last-roll", self["last_roll"],
         "--use-commit-queue",
         self["roll"],
       ]
-      if self._options.sheriff:
-        args.append("--sheriff")
       if self._options.dry_run:
         args.append("--dry-run")
       if self._options.work_dir:
         args.extend(["--work-dir", self._options.work_dir])
       if self._options.chromium_roll_json_output:
         args.extend(["--json-output", self._options.chromium_roll_json_output])
       self._side_effect_handler.Call(chromium_roll.ChromiumRoll().Run, args)
 
 
 class AutoRoll(ScriptsBase):
@@ skipping 24 matching lines @@
 
   def _Steps(self):
     return [
       DetectLastRoll,
       RollChromium,
     ]
 
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(AutoRoll().Run())