quay remote: allowlist oauth2-proxy images

Adds the ^oauth2-proxy/ pattern to the quay.io remote so the
artifactapi caching proxy will serve quay.io/oauth2-proxy/oauth2-proxy.
Needed so the arrproxy oauth2-proxy sidecar can pull the real upstream
quay.io address via the rke2 registries.yaml mirror.

config/remote_docker/quay.yaml

@@ -7,3 +7,4 @@ patterns:
   - "^brancz/kube-rbac-proxy"
   - "^cephcsi/cephcsi"
   - "^jetstack/cert-manager-"
+  - "^oauth2-proxy/"