Update OWNERS file

zhaojiac@ is no longer in Android, removing him from owners list and add
myself.

Test: th
Change-Id: I0521d8689e52285e06d3989c4f20d87aca8450f8
diff --git a/OWNERS b/OWNERS
index 79dd9f7..0e289d6 100644
--- a/OWNERS
+++ b/OWNERS
@@ -2,4 +2,5 @@
 enh@google.com
 nhdo@google.com
 xunchang@google.com
-zhaojiac@google.com
+zhangkelvin@google.com
+