Decomissioned PR-Custom-Review (#2503)

This PR decomissions
[`PR-Custom-Review`](https://github.com/paritytech/pr-custom-review) in
replacement for
[`Review-bot`](https://github.com/paritytech/review-bot).

.github/workflows/pr-custom-review.yml

@@ -1,46 +0,0 @@
-name: Assign reviewers
-
-on:
-  pull_request:
-    branches:
-      - master
-      - main
-    types:
-      - opened
-      - reopened
-      - synchronize
-      - review_requested
-      - review_request_removed
-      - ready_for_review
-      - converted_to_draft
-  pull_request_review:
-  merge_group:
-
-jobs:
-  pr-custom-review:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Skip merge queue
-        if: ${{ contains(github.ref, 'gh-readonly-queue') }}
-        run: exit 0
-      - name: Skip if pull request is in Draft
-        # `if: github.event.pull_request.draft == true` should be kept here, at
-        # the step level, rather than at the job level. The latter is not
-        # recommended because when the PR is moved from "Draft" to "Ready to
-        # review" the workflow will immediately be passing (since it was skipped),
-        # even though it hasn't actually ran, since it takes a few seconds for
-        # the workflow to start. This is also disclosed in:
-        # https://github.community/t/dont-run-actions-on-draft-pull-requests/16817/17
-        # That scenario would open an opportunity for the check to be bypassed:
-        # 1. Get your PR approved
-        # 2. Move it to Draft
-        # 3. Push whatever commits you want
-        # 4. Move it to "Ready for review"; now the workflow is passing (it was
-        #    skipped) and "Check reviews" is also passing (it won't be updated
-        #    until the workflow is finished)
-        if: github.event.pull_request.draft == true
-        run: exit 1
-      - name: pr-custom-review
-        uses: paritytech/pr-custom-review@master
-        with:
-          checks-reviews-api: http://pcr.parity-prod.parity.io/api/v1/check_reviews