ci: pin @capacitor/core to match matrix version

create-app scaffolds with @capacitor/core@latest which conflicts when
installing @capacitor/ios at an older major version.

Author: j3k0

.github/workflows/build-capacitor-ios.yml

@@ -40,7 +40,8 @@ jobs:
           npm install -g @capacitor/cli@${{ matrix.capacitor-version }}
           npx @capacitor/create-app test-cap-app --name TestApp --app-id com.test.app
           cd test-cap-app
-          npm install @capacitor/ios@${{ matrix.capacitor-version }}
+          # Pin all Capacitor deps to the same major version
+          npm install @capacitor/core@${{ matrix.capacitor-version }} @capacitor/ios@${{ matrix.capacitor-version }}
           npx cap add ios
           # Log which package manager was used
           if [ -d ios/App/CapApp-SPM ]; then