`match init` assumes a default branch of `master` when using git storage, which is no longer the Github default

New Issue Checklist

• Updated fastlane to the latest version
• I read the Contribution Guidelines
• I read docs.fastlane.tools
• I searched for existing GitHub issues

Issue Description

After setting up a new app recently with fastlane match I noticed the default Matchfile generate assumes GitHub's default branch to be master, not main. main is now the default for all new GitHub repositories - see https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-branches#about-the-default-branch and this caused a small amount of reconfiguration work.

I'd suggest we should now be prompting for a default branch name on match init, and fallback to master if none is provided.

If there's agreement, happy to PR that.

Command executed

fastlane match init

Complete output when running fastlane, including the stack trace and command used

• N / A

Environment

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