Request reviews automatically using CODEOWNERS

This then also automatically works for the PRs opened by the retire.sh
script

Author: infinisil

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @NixOS/commit-bit-delegation

.github/workflows/sync.yml

@@ -47,5 +47,4 @@ jobs:
           branch: create-pull-request/sync
           title: Automated sync
           body: This is an automated PR to sync the member list in this repository to match the GitHub team members. This PR can be merged without taking any further action.
-          team-reviewers: commit-bit-delegation