ci: pin PR xcode version [skip ci]

Author: edusperoni

.github/workflows/pull_request.yml

@@ -11,7 +11,7 @@ jobs:
     steps:
       - uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: latest-stable
+          xcode-version: "^15.0"
       - uses: actions/checkout@v3
         with:
           fetch-depth: 0