Update .asf.yaml (#701)

As requested by Fokko:
Could you raise a PR to remove Xuanwo and Renjie as a collaborator (they are committer now, so the collaborator right are implied), and add you next to JanKaul?

Author: c-thiel

.asf.yaml

@@ -48,9 +48,8 @@ github:
     issues: true
     projects: true
   collaborators:
-    - Xuanwo
-    - liurenjie1024
     - JanKaul
+    - c-thiel
   ghp_branch: gh-pages
   ghp_path: /