Update AppStoreConnect Documentation to account for language change

[Adam0101]

Primary local of "English" doesn't work anymore now that it's "English (U.S.) on App Store Connect.

Changed to en-us

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 see several green ci/circleci builds in the "All checks have passed" section of my PR (connect CircleCI to GitHub if not)
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.
• I've added or updated relevant unit tests.

Motivation and Context

Description

Testing Steps