Revert "git-cache: don't limit pack files to 2GiB."

This reverts commit 82ae4b4b.

Reason for revert: didn't help. Something else limits 'git gc' by 2GB.
However, even so, total amount of .pack files for chromium/src is <7.5GB.

Original change's description:
> git-cache: don't limit pack files to 2GiB.
>
> This is only relevant to 1 builder which updates git cache bundles.
> Since some time in 2018-2019, it started creating several 2GiB packs
> for chromium/src. I verified that the setting affecting it is
>   core.deltaBaseCacheLimit
>
> Log file of a build which I observed while ssd-ed into the machine (internal):
>   https://logs.chromium.org/logs/infra-internal/buildbucket/cr-buildbucket.appspot.com/8901682638839779824/+/steps/Updating_https:__chromium.googlesource.com_chromium_src/0/stdout
> Git version: version:2.21.0.chromium16
>
> R=​ehmaldonado
>
> Change-Id: I52cadfb9f34faea09a57d53387cab7e0538362b9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1818076
> Auto-Submit: Andrii Shyshkalov <tandrii@google.com>
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

TBR=tandrii@google.com,ehmaldonado@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I24915555c703bc92fda921524820405de5d69f7d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1817101Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

git_cache.py

@@ -592,12 +592,6 @@ class Mirror(object):
       return
 
     # Run Garbage Collect to compress packfile.
-    # It appears core.deltaBaseCacheLimit restricts the file size of the pack
-    # files produced, while we want 1 big pack file for efficiency.
-    try:
-      self.RunGit(['config', '--unset-all', 'core.deltaBaseCacheLimit'])
-    except subprocess.CalledProcessError:
-      pass  # Nothing to unset is fine.
     gc_args = ['gc', '--prune=all']
     if gc_aggressive:
       gc_args.append('--aggressive')