Pinning to Xcode 15.4 doesn't actually pin and the simulator is running on iOS 18 beta

[yarneo]

Run mxcl/xcodebuild@v2.0
  with:
    xcode: 15.4.0
    platform: iOS
    code-coverage: true
    action: test
    scheme: Catalog
    warnings-as-errors: false
    verbosity: xcpretty
    upload-logs: on-failure
» Selected Xcode 15.4.0
Creating provisioning profiles
xcodebuild test
  --- xcodebuild: WARNING: Using the first of multiple matching destinations:
  { platform:iOS Simulator, id:80649341-558[2](https://github.com/.../actions/runs/9566252578/job/26371076440#step:3:2)-4C55-8B4F-067A86FFEACE, OS:18.0, name:iPhone SE ([3](https://github.com/.../actions/runs/9566252578/job/26371076440#step:3:3)rd generation) }