Update OWNERS file (#212)

Add Karan Chauhan <kachau@redhat.com>
Remove Martin Povolny <mpovolny@redhat.com> as he is less active
with this project.

Author: Karanraj Chauhan

OWNERS

@@ -5,4 +5,4 @@ approvers:
   - hemajv
   - sesheta
 reviewers:
-  - martinpovolny
+  - chauhankaranraj