Build: Switch macos-13 (Intel) to macos-latest (macOS-15-arm64)

Ref actions/runner-images#13046.

Author: Krinkle

.github/workflows/CI.yaml

@@ -39,7 +39,7 @@ jobs:
             script: npm run test-nolint
 
           - name: "macOS: Node 18"
-            os: macos-13
+            os: macos-latest
             node: 18.x
             script: npm run test-nolint