Remove directxman12 from OWNERS

DirectXMan12 · DirectXMan12 · commit 5a3896c2deb2 · 2021-06-14T15:43:16.000-07:00
As per https://groups.google.com/g/kubebuilder/c/-5hOFa_adr4/m/Sp_Zb755AwAJ, directxman12 is stepping down.
diff --git a/OWNERS_ALIASES b/OWNERS_ALIASES
@@ -2,7 +2,6 @@
 
 aliases:
   kubebuilder-admins:
-    - DirectXMan12
     - droot
     - Liujingfang1
     - mengqiy
