CI: Use free macos-14 runners for aarch64-apple-* targets.

This allows contributors to run the full CI without having to buy
GitHub credits. Previously contributors' CI jobs for these targets
would fail if they didn't have GitHub Actions credits to spend on
macos-13-xlarge runners.

Author: briansmith

.github/workflows/ci.yml

@@ -173,22 +173,10 @@ jobs:
 
         include:
           - target: aarch64-apple-darwin
-            mode: --release
-            rust_channel: stable
-            host_os: macos-13-xlarge # This always costs $$$ but can actually run the tests.
-
-          - target: aarch64-apple-darwin
-            rust_channel: 1.61.0
-            host_os: macos-13 # This can use free credits...
-            cargo_options: --no-run # ... but can't run the tests.
-
-          - target: aarch64-apple-darwin
-            mode: # debug
-            host_os: macos-13 # This can use free credits...
-            cargo_options: --no-run # ... but can't run the tests.
+            host_os: macos-14
 
           - target: aarch64-apple-ios
-            host_os: macos-13
+            host_os: macos-14
             # TODO: Run in the emulator.
             cargo_options: --no-run