Remove a redundant warning already covered by the commit messages check

Signed-off-by: Rémy Coutable <remy@rymai.me>

danger/metadata/Dangerfile

@@ -40,10 +40,3 @@ has_pick_into_stable_label = gitlab.mr_labels.find { |label| label.start_with?('
 if gitlab.branch_for_base != "master" && !has_pick_into_stable_label && !helper.security_mr?
   warn "Most of the time, merge requests should target `master`. Otherwise, please set the relevant `Pick into X.Y` label."
 end
-
-if gitlab.mr_json['title'].length > 72
-  warn 'The title of this merge request is longer than 72 characters and ' \
-    'would violate our commit message rules when using the Squash on Merge ' \
-    'feature. Please consider adjusting the title, or rebase the ' \
-    "commits manually and don't use Squash on Merge."
-end