Use latest Xcode version in GitHub Actions

Author: rechsteiner

.github/workflows/parchment.yml

@@ -4,6 +4,9 @@ jobs:
   build:
     runs-on: macos-latest
     steps:
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: latest-stable
       - uses: actions/checkout@v3
       - name: Unit Tests
         run: xcodebuild -project Parchment.xcodeproj -scheme "Parchment" -sdk iphonesimulator -destination 'platform=iOS Simulator,name=iPhone 15 Pro,OS=17.5' test