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

Match generates and overwrites a README.md file in each repository in which it's deployed. We've often made the mistake of editing the README with our own information only to have it overwritten. Moving the note about the README being auto-generated to the top of the file will help the warning stand out to potential editors.

Description

This is a simple text change that doesn't affect the performance of any fastlane tools.

Testing Steps

Testing was done by viewing the changes in a GitHub markdown renderer: