Update xcode to 14c18 for host only bots (#125211)

With https://flutter-review.googlesource.com/c/recipes/+/42160, we are
ready to make all tests consistent with xcode 14c18.

> auto label is removed for flutter/flutter, pr: 125211, due to This PR has not met approval requirements for merging. Changes were requested by {jmagman}, please make the needed changes and resubmit this PR. You have project association MEMBER and need 1 more review(s) in order to merge this PR.
> 
> * Merge guidelines: You need at least one approved review if you are already a MEMBER or two member reviews if you are not a MEMBER before re-applying the autosubmit label. **Reviewers**: If you left a comment approving, please use the "approve" review action instead.

Sounds an auto-submit bug. Manually submit.