update runner to macOS 26 runner from old 12. (#48)

Author: Sajjon

.github/workflows/swift.yml

@@ -15,7 +15,7 @@ concurrency:
 
 jobs:
   linting:
-    runs-on: macos-12
+    runs-on: macos-26
     steps:
       - uses: actions/checkout@v3
       - name: "Run Lint"
@@ -25,7 +25,7 @@ jobs:
           swiftformat . --lint
 
   unittest:
-    runs-on: macos-12
+    runs-on: macos-26
     needs:
       - linting
     strategy: