Make open PR check stricter

Author: StanFromIreland

.github/workflows/check-for-updates.yml

@@ -21,7 +21,8 @@ jobs:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           PR_EXISTS=$(gh pr --repo "$GITHUB_REPOSITORY" \
-                      list --search "Update tzdata to version" \
+                      list --state open \
+                      --search 'in:title "Update tzdata to version"' \
                       --json number --jq '.[] | .number')
           if [ -n "$PR_EXISTS" ]; then
             echo "A PR updating the tzdata version already exists: https://github.com/python/tzdata/pulls/${PR_EXISTS}"