Move checks back to default runners

These jobs are not rate-limiting so we don't need to run them on larger runners.

Author: henrymercer

.github/workflows/__all-platform-bundle.yml

@@ -2,8 +2,7 @@ name: "All-platform bundle"
 description: "Tests using an all-platform CodeQL Bundle"
 operatingSystems:
   - ubuntu
-  - os: macos
-    runner-image: macos-latest-xlarge
+  - macos
   - windows
 versions:
   - nightly-latest

.github/workflows/__swift-custom-build.yml

@@ -5,8 +5,7 @@ versions:
   - default
   - nightly-latest
 operatingSystems:
-  - os: macos
-    runner-image: macos-latest-xlarge
+  - macos
 installGo: true
 installDotNet: true
 env: