[0.70] Backport #10440 & #10444 (#10458)

* Fix CI warnings on github returning 403's (#10440)

* Update to later Mac version, there is a brown-out before the 9/30 deprecation fo 10.15 (#10444)

.ado/jobs/macos-tests.yml

@@ -7,7 +7,7 @@ jobs:
       - template: ../variables/shared.yml
       - name: BUILDSECMON_OPT_IN
         value: true
-    pool: {vmImage: macOS-10.15}
+    pool: {vmImage: macOS-12}
     steps:
       - template: ../templates/checkout-shallow.yml
 

.unbroken_exclusions

@@ -1,3 +1,6 @@
+URL not found https://docs.github.com/pull-requests/collaborating-with-pull-requests/getting-started/about-collaborative-development-models#fork-and-pull-model while parsing CONTRIBUTING.md (HTTP 403)
+URL not found https://docs.github.com/pull-requests/collaborating-with-pull-requests/working-with-forks/about-forks while parsing CONTRIBUTING.md (HTTP 403)
+URL not found https://docs.github.com/get-started/quickstart while parsing CONTRIBUTING.md (HTTP 403)
 !**/node_modules
 !vnext/packages
 !vnext/ReactCopies
@@ -16,4 +19,4 @@
 !packages/@rnw-scripts/doxysaurus/node_modules
 !packages/@rnw-scripts/format-files/node_modules
 !packages/@rnw-scripts/promote-release/node_modules
-!.github/ISSUE_TEMPLATE
+!.github/ISSUE_TEMPLATE