Revert "Set blame.ignoreRevsFile to .git-blame-ignore-revs."

This reverts commit 9bbf9b0541.

Reason for revert: breaks for repos that don't have 
.git-blame-ignore-revs file. See http://b/368562244

Original change's description:
> Set blame.ignoreRevsFile to .git-blame-ignore-revs.
>
> This basically brings the functionality of git hyper-blame to git blame
> by default and is supported since git 2.23.
>
> Bug: none
> Change-Id: I2023669deac999ef31d0e094e79d7214168acb63
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5838110
> Auto-Submit: Peter Kasting <pkasting@chromium.org>
> Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
> Commit-Queue: Peter Kasting <pkasting@chromium.org>
> Reviewed-by: Gavin Mak <gavinmak@google.com>

Bug: b/368562244
Change-Id: Iae38a25390dd64f26ece9178856c251c4e2c22a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5883673
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>

gclient_scm.py

@@ -671,12 +671,6 @@ class GitWrapper(SCMWrapper):
                 # the cache to set and unset consecutively.
                 config_updates = []
 
-                if scm.GIT.GetConfig(
-                        args[0].checkout_path,
-                        'blame.ignorerevsfile') != '.git-blame-ignore-revs':
-                    config_updates.append(
-                        ('blame.ignoreRevsFile', '.git-blame-ignore-revs'))
-
                 ignore_submodules = scm.GIT.GetConfig(args[0].checkout_path,
                                                       'diff.ignoresubmodules',
                                                       None, 'local')