Remove Auto Request Review workflow in favor of CODEOWNERS (#10018)

.github/workflows/auto_request_review.yml

@@ -1,22 +0,0 @@
----
-name: "Auto Request Review"
-
-on:
-  pull_request_target:
-    types: [opened, ready_for_review, reopened]
-
-permissions:
-  contents: read
-  pull-requests: write
-
-jobs:
-  auto-request-review:
-    if: github.repository == 'velero-io/velero'
-    name: Auto Request Review
-    runs-on: ubuntu-latest
-    steps:
-      - name: Request a PR review based on files types/paths, and/or groups the author belongs to
-        uses: necojackarc/auto-request-review@v0.13.0
-        with:
-          config: .github/auto-assignees.yml
-          token: ${{ secrets.GITHUB_TOKEN }}