Added deprecation block for GitLab.com internal vis disabled to 12.2 release post

PMM: @johnjeremiah Tech Writing: @eread

Content checklist

• YML filled out for feature
• Description is informative and focuses on the problem we're solving and the value we're delivering
• Documentation is updated and linked
• Screenshot is included (optional, but encouraged)

Review

When the above is complete and the content is ready for review, it should be reviewed by Product Marketing and Tech Writing:

• PMM review
• Tech writing

Checklist for reference

• Make sure feature description is positive and cheerful
• Check Feature name
• Check Feature availability (Core, Starter, Premium, Ultimate badges)
• Feature is added to data/features.yml (with accompanying screenshots)
• Check all images size < 300KB (compressed, max width 1000 pixels)
• Check that documentation is updated and easy to understand
• Check Documentation links (all feature blocks contain documentation_link)
• Run the content through an automated spelling and grammar check
• Validate all links are functional

Release post

Intended to be part of !27164 (merged) as per the new contribution instructions.