Update validate-pr-title.yml

Signed-off-by: John McCall <john@overturemaps.org>

Author: lowlydba

.github/workflows/validate-pr-title.yml

@@ -65,10 +65,6 @@ jobs:
             SECURITY
             INVESTIGATION
 
-          # Validate single-commit PRs too, since GitHub may suggest the commit
-          # message instead of the PR title when squash-merging.
-          validateSingleCommit: true
-
           # Allow [WIP] prefix for draft work on repos without draft PR support.
           wip: true