CI: PrAssignee.yml: don't auto-retry on 404

Author: DilumAluthge

.github/workflows/PrAssignee.yml

@@ -38,7 +38,7 @@ jobs:
         uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
         with:
           retries: 5 # retry GitHub API requests up to 5 times, with exponential backoff
-          retry-exempt-status-codes: 403
+          retry-exempt-status-codes: "403,404"
           script: |
             const oldPrAssignees = context.payload.pull_request.assignees
               .map(obj => obj.login)