Revert of [ObjC ARC] Converts ios/chrome/browser/prefs:prefs to ARC.Automatically generated ARCMigrate comm… (patchset #1 id:1 of https://codereview.chromium.org/2506153004/ )

Reason for revert:
Breaks roll. Details sent via email.

Original issue's description:
> [ObjC ARC] Converts ios/chrome/browser/prefs:prefs to ARC.
>
> Automatically generated ARCMigrate commit
> Notable issues:None
> BUG=624363
> TEST=None
>
> Committed: https://crrev.com/dc7a6cd5cc6d8b07647c2876f1534a46fccb6aa1
> Cr-Commit-Position: refs/heads/master@{#433243}

TBR=noyau@chromium.org,stkhapugin@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTRY=true
BUG=624363

Review-Url: https://codereview.chromium.org/2511883007
Cr-Commit-Position: refs/heads/master@{#433383}
3 files changed