fix: set WORKER_URL in workflow

Worker URL was empty, causing curl requests to fail

Author: DaleSeo

.github/workflows/check-prs.yaml

@@ -34,7 +34,7 @@ jobs:
       - name: Check Week settings for all PRs
         run: |
           prs='${{ steps.get-prs.outputs.prs }}'
-          WORKER_URL=""
+          WORKER_URL="https://dalestudy.daleseo.workers.dev"
           repo_owner="${{ github.repository_owner }}"
           repo_name="${{ github.event.repository.name }}"