[cq] Automatically use the same bots for git cl try.

Depot tools now uses the project's cq.cfg by default on
git cl try, if no other method is specified.

Based on:
https://codereview.chromium.org/1579423004/
https://codereview.chromium.org/1587893003/

BUG=chromium:565952
TBR=tandrii@chromium.org
LOG=n
NOTRY=true

Review URL: https://codereview.chromium.org/1583233002

Cr-Commit-Position: refs/heads/master@{#33289}

PRESUBMIT.py

@@ -275,28 +275,3 @@ def CheckChangeOnCommit(input_api, output_api):
         input_api, output_api,
         json_url='http://v8-status.appspot.com/current?format=json'))
   return results
-
-
-def GetPreferredTryMasters(project, change):
-  return {
-    'tryserver.v8': {
-      'v8_linux_rel_ng': set(['defaulttests']),
-      'v8_linux_dbg_ng': set(['defaulttests']),
-      'v8_linux_nodcheck_rel': set(['defaulttests']),
-      'v8_linux_gcc_compile_rel': set(['defaulttests']),
-      'v8_linux64_rel_ng': set(['defaulttests']),
-      'v8_linux64_asan_rel': set(['defaulttests']),
-      'v8_linux64_avx2_rel': set(['defaulttests']),
-      'v8_win_rel_ng': set(['defaulttests']),
-      'v8_win_compile_dbg': set(['defaulttests']),
-      'v8_win_nosnap_shared_compile_rel': set(['defaulttests']),
-      'v8_win64_rel_ng': set(['defaulttests']),
-      'v8_mac_rel': set(['defaulttests']),
-      'v8_linux_arm_rel': set(['defaulttests']),
-      'v8_linux_arm64_rel': set(['defaulttests']),
-      'v8_linux_mipsel_compile_rel': set(['defaulttests']),
-      'v8_linux_mips64el_compile_rel': set(['defaulttests']),
-      'v8_android_arm_compile_rel': set(['defaulttests']),
-      'v8_linux_chromium_gn_rel': set(['defaulttests']),
-    },
-  }