Update the default reviewers (#5751)

Update the group members of "maintainers" and "tech-writer" to reflect
the change in the team.
As for the group "tech-writer" I just selected a few members from
maintains team who has been working on velero for a relatively longer
time.

Signed-off-by: Daniel Jiang <jiangd@vmware.com>

.github/auto-assignees.yml

@@ -9,7 +9,6 @@ reviewers:
 
   groups:
     maintainers:
-      - dsu-igeek
       - sseago
       - reasonerjt
       - ywk253100
@@ -19,7 +18,10 @@ reviewers:
       - Lyndon-Li
 
     tech-writer:
-      - a-mccarthy
+      - sseago
+      - reasonerjt
+      - ywk253100
+      - Lyndon-Li
 
 files:
   'site/**':