rem: ci: Drop Danger check related to pre-release testing

With the advent of the new development model involving security-*
branches and autorebasing, the value added by the pre-release testing
mechanism dropped drastically.  The only remaining benefit of
pre-release testing is flagging in-progress security fixes targeting
open source branches that conflict with the corresponding bind-9.x-sub
branches.  However, such conflicts are a rare occurrence and can be
handled after merging anyway.

Remove the Danger check related to pre-release testing.

Merge branch 'michal/drop-danger-check-related-to-pre-release-testing' into 'main'

See merge request isc-projects/bind9!12313