dont force the use of arm64 builders in mac13-arm64

Previously added arm64 to settings in order to fix the issue,
but there are currently no builders for wptrunner using arm64, so just
remove this for now. The mac-13 base builder is working now so the
arm-64 might work without this cpu expectation as well.

Change-Id: I4e957f26d308cf635e67ba3e4453b940c1948b59
Bug: 1425592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4353932


Commit-Queue: Nihar Damarasingu <nihardamar@google.com>
Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1119481}