Automatically remove unlicensed reviewer from PR reviewers list

Users are getting a The user <username> cannot participate in the pull request as they are not a licensed user when creating a PR.

Below is the current behavior:

• If the unlicensed reviewer is part of a Reviewer Group, that reviewer is automatically removed from the reviewer list of the PR once the error pops up. You could then click the Create button again to create the Pull Request.
• If the unlicensed reviewer is part of the Default Reviewers list, that reviewer is not removed from the reviewer list once the error pops up. You need to remove the user manually before clicking the Create button.

Bitbucket should automatically remove the unlicensed reviewers from the list, rather than asking the end user to remove them.