Edit Danger message to allow backport to versions in extended maintenance policy

Context

From gitlab-com/content-sites/handbook!15114 (comment 2670834474)

As we extend the maintenance policy to allow bug fixes to be backported to N, N-1, and N-2 stable branches, we need to edit the Danger messages posted on merge requests targeting stable branches outside of the current policy for bug fixes.

When a backport to an older version than the current version is opened (e.g. 18.1), a message is posted by Danger asking them to open an exception request like so:

Link

This logic won't apply with the new maintenance policy and should be updated

Exit criteria

• Create MR to update the Danger warning message to allow backports to versions in the extended maintenance policy gitlab-org/gitlab!204392 (merged)
• Backport MR to maintained branches gitlab-org/gitlab!204767 (merged) and gitlab-org/gitlab!204768 (merged)