Update doc about Debian version

Before !823 we
specified which debian version has this.

closes #4481
5 jobs for docs/4481-follow-up-from-docs-clarify-the-requirements-for-pinning in 4 minutes and 26 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Prebuild
passed #252302677
check feature flags docs

00:01:20

manual #252302651
allowed to fail manual
review-docs-deploy
 
  Test
passed #252302685
docs lint

00:01:35

passed #252302683
allowed to fail
license_management

00:03:06

 
  Cleanup
manual #252302688
allowed to fail manual
review-docs-cleanup