bug(ci): remove unused var from dependabot

Author: dshemetov

.github/workflows/dependabot-assignments.yml

@@ -20,7 +20,5 @@ jobs:
             -H "Accept: application/vnd.github+json" \
             -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}"\
             -H "X-GitHub-Api-Version: 2022-11-28" \
-            https://api.github.com/repos${{ github.owner }}/${{ github.repository }}/pulls/${{ github.event.pull_request.number }}/requested_reviewers \
+            https://api.github.com/repos${{ github.owner }}/${{ github.repository }}/pulls/${{github.event.pull_request.number}}/requested_reviewers \
             -d '{"team_reviewers":["code-reviewers"]}'
-        env:
-          PR_URL: ${{github.event.pull_request.html_url}}