Exclude policy_repair QQ test on mixed versions

[LoisSotoLopez]

Proposed Changes

As suggested here #12412 (comment) the recently merged QQ policy repair mechanism included some tests that are not passing in the CI for mixed versions clusters. This PR prevents that test execution for the mixed versions cluster tests.

Types of Changes

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• I have added tests that prove my fix is effective or that my feature works
• All tests pass locally with my changes
• If relevant, I have added necessary documentation to https://github.com/rabbitmq/rabbitmq-website
• If relevant, I have added this change to the first version(s) in release-notes that I expect to introduce it

Further Comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution
you did and what alternatives you considered, etc.

[michaelklishin]

Moved to #12666 so that tests have access to secrets.

[mergify]

⚠️ The sha of the head commit of this PR conflicts with #12666. Mergify cannot evaluate rules on this PR. ⚠️