ci: Mac runner removal (#1144)

Author: Jaskowicz1

.github/workflows/ci.yml

@@ -111,10 +111,10 @@ jobs:
     strategy:
       fail-fast: false # Don't fail everything if one fails. We want to test each OS/Compiler individually
       matrix:
-        # arm64 is a self-hosted runner on a Mac M2 Mini, ran inside a virtual machine by Archie Jaskowicz.
+        # arm64 is a self-hosted runner on a Mac M2 Mini, ran inside a virtual machine by Archie Jaskowicz. NOTE: This runner no longer exists. It may come back in a few months.
         cfg:
           - { arch: 'x64', concurrency: 3, os: macos-latest, cpp-version: clang++-14, cmake-flags: ''}
-          - { arch: 'arm64', concurrency: 2, os: [self-hosted, ARM64, macOS], cpp-version: clang++-15, cmake-flags: ''}
+#          - { arch: 'arm64', concurrency: 2, os: [self-hosted, ARM64, macOS], cpp-version: clang++-15, cmake-flags: ''}
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@a4aa98b93cab29d9b1101a6143fb8bce00e2eac4 # v2.7.1