presubmit: Check freeze on commit only

Blocking developers from uploading (even WIP) CLs to Gerrit during a
production freeze seems unnecessary and too strict. By turning
CheckFreeze into an "on commit" presubmit check, developers will be able
to upload CLs for review, but not submit them during a freeze.

Change-Id: I199c6c3edcbe1e2d69e4caf74f2d4c9060e98e54
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5932363
Auto-Submit: Philipp Wollermann <philwo@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>

PRESUBMIT.py

@@ -193,5 +193,5 @@ def CheckPatchFormatted(input_api, output_api):
                                                        check_clang_format=False)
 
 
-def CheckFreeze(input_api, output_api):
+def CheckFreezeOnCommit(input_api, output_api):
     return input_api.canned_checks.CheckInfraFreeze(input_api, output_api)