Update Issue Xcode placeholder to a supported version (#12778)

Author: paulb777

.github/ISSUE_TEMPLATE/BUG_REPORT.yml

@@ -46,7 +46,7 @@ body:
     attributes:
       label: Xcode Version
       description: What version of Xcode is being used?
-      placeholder: "14.3"
+      placeholder: "15.3"
     validations:
       required: true
   - type: dropdown