[pgo] set mac ci symbol levels to 1

Help debug benchmark failures.

Bug: b/333549704
Change-Id: Ie27f26268923336146049600eee53767abdc2ba0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5484306


Commit-Queue: Scott Violet <sky@chromium.org>
Commit-Queue: Jeff Yoon <jeffyoon@google.com>
Auto-Submit: Jeff Yoon <jeffyoon@google.com>
Reviewed-by: Haiyang Pan <hypan@google.com>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1291981}