fix: make the pbxproject fastlane compatible

[DimitarTachev]

PR Checklist

• [x] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [x] There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• [x] You have signed the CLA.
• [x] All existing tests are passing: https://github.com/NativeScript/ios-runtime/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• [ ] Tests for the changes are included.

What is the current behavior?

The disable_automatic_code_signing method in fastlane fails with: Seems to be a very old project file format - please open your project file in a more recent version of Xcode

What is the new behavior?

The project can be processed by the fastlane tools.