Fix GitHub Actions workflow: Simplify hashFiles() syntax

- Change from hashFiles('Package.swift', 'Package@*.swift') to hashFiles('Package.swift')
- Fixes 'template is not valid' error on macOS runner
- hashFiles() doesn't support multiple glob patterns in GitHub Actions

Author: coenttb

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: .build
-          key: macos-swift62-spm-${{ hashFiles('Package.swift', 'Package@*.swift') }}
+          key: macos-swift62-spm-${{ hashFiles('Package.swift') }}
           restore-keys: |
             macos-swift62-spm-