[gym] update available export_methods to match xcodebuild command

[rogerluan]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

Resolves #17918

Description

According to xcodebuild -help:

method : String

    Describes how Xcode should export the archive. Available options: app-store, validation, package, ad-hoc, enterprise, development, developer-id, and mac-application. The list of options varies based on the type of archive. Defaults to development.

This PR updates our client validation to allow all those values.

Testing Steps

To test this branch, modify your Gemfile as:

gem "fastlane", :git => "https://github.com/fastlane/fastlane.git", :branch => "rogerluan-update-available-export-methods"

And run bundle install to apply the changes.

[minuscorp]

LGTM! 🚀

[joshdholtz]

Looks great to me! Thanks again for another PR ❤️

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.172.0 🚀