[release] Roll the more frequently updated lkgr ref into chromium.

NOTRY=true

Review URL: https://codereview.chromium.org/1394453002

Cr-Commit-Position: refs/heads/master@{#31141}

tools/release/auto_push.py

@@ -46,12 +46,12 @@ class Preparation(Step):
 
 
 class FetchCandidate(Step):
-  MESSAGE = "Fetching V8 roll ref."
+  MESSAGE = "Fetching V8 lkgr ref."
 
   def RunStep(self):
     # The roll ref points to the candidate to be rolled.
-    self.Git("fetch origin +refs/heads/roll:refs/heads/roll")
-    self["candidate"] = self.Git("show-ref -s refs/heads/roll").strip()
+    self.Git("fetch origin +refs/heads/lkgr:refs/heads/lkgr")
+    self["candidate"] = self.Git("show-ref -s refs/heads/lkgr").strip()
 
 
 class LastReleaseBailout(Step):

tools/release/test_scripts.py

@@ -1061,8 +1061,8 @@ TBR=g_name@chromium.org,reviewer@chromium.org"""
   def testAutoPush(self):
     self.Expect([
       Cmd("git fetch", ""),
-      Cmd("git fetch origin +refs/heads/roll:refs/heads/roll", ""),
-      Cmd("git show-ref -s refs/heads/roll", "abc123\n"),
+      Cmd("git fetch origin +refs/heads/lkgr:refs/heads/lkgr", ""),
+      Cmd("git show-ref -s refs/heads/lkgr", "abc123\n"),
       Cmd("git fetch origin +refs/tags/*:refs/tags/*", ""),
       Cmd("git tag", self.TAGS),
       Cmd("git log -1 --format=%H 3.22.4", "release_hash\n"),