test: move CI to macos-12 runners

[mikehardy]

Description

this should probe the python2/python3 failure in ios config infra

Related issues

Related #6226
Related #6203

Also this is a pre-requisite for firebase-ios-sdk v9, since it requires Xcode 13.3+, and that transitively requires macos-12

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

---

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Name	Status	Preview	Updated
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[codecov]

Codecov Report

Merging #6235 (a7e3b8f) into main (f26482d) will not change coverage.
The diff coverage is n/a.

❗ Current head a7e3b8f differs from pull request most recent head a07caa2. Consider uploading reports for the commit a07caa2 to get more accurate results

@@            Coverage Diff            @@
##               main    #6235   +/-   ##
=========================================
  Coverage     53.40%   53.40%           
  Complexity      643      643           
=========================================
  Files           208      208           
  Lines         10302    10302           
  Branches       1633     1633           
=========================================
  Hits           5501     5501           
  Misses         4543     4543           
  Partials        258      258