github: workflows: compliance: remove ineffective check

The commit 7b1e610c ("ci: move PR body check to a different workflow")
moved the step this depends on to the do_not_merge workflow,
so it no longer has any effect.

This extra message was initially added to the fail step to make it
easier to spot the issue. But I don't think it's necessary
in the do_not_merge workflow either now.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>