Fix wording in Danger warning about MRs to non-master

If it's most of the time, then it's not all.

danger/metadata/Dangerfile

@@ -21,5 +21,5 @@ end
 has_pick_into_stable_label = gitlab.mr_labels.find { |label| label.start_with?('Pick into') }
 
 if gitlab.branch_for_base != "master" && !has_pick_into_stable_label
-  warn "Most of the time, all merge requests should target `master`. Otherwise, please set the relevant `Pick into X.Y` label."
+  warn "Most of the time, merge requests should target `master`. Otherwise, please set the relevant `Pick into X.Y` label."
 end