Revert "Temporarily return ios-fieldtrial-rel to targeting Mac-13|Mac-14 until bots upgrade"

This reverts commit 4b3d44bc.

Reason for revert: Bots have now been upgraded to Mac-14

Original change's description:
> Temporarily return ios-fieldtrial-rel to targeting Mac-13|Mac-14 until bots upgrade
>
> Bug: 345748239
> Change-Id: Ib336a58a1ba9ee9e1a89a773392401976795fde9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5605637


> Reviewed-by: Yue She <yueshe@google.com>
> Commit-Queue: Will Yeager <wyeager@google.com>
> Reviewed-by: Zhaoyang Li <zhaoyangli@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1312203}

Bug: 345748239
Change-Id: I131a73b79beb0b306d3d1c54809c709abe7026f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5615210


Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Yue She <yueshe@google.com>
Commit-Queue: Will Yeager <wyeager@google.com>
Cr-Commit-Position: refs/heads/main@{#1312773}