[BUG](ci) Must use strings here, not numbers

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

Author: lowlydba

.github/workflows/overture-projection.yml

@@ -77,7 +77,7 @@ on:
       pr_number:
         description: PR number to review
         required: true
-        type: number
+        type: string
       devex_ref:
         description: omf-devex ref to load skills from
         required: false