mte: add nnk@google.com to OWNERS

That way I can help with reviews and other MTE changes.

Test: not needed. OWNERS file change only
Change-Id: I1fb75c2e1347c4085eb614f858b4fb57dd462ad1
diff --git a/mte/OWNERS b/mte/OWNERS
index 929e941..66a1635 100644
--- a/mte/OWNERS
+++ b/mte/OWNERS
@@ -2,3 +2,4 @@
 pcc@google.com
 mitchp@google.com
 fmayer@google.com
+nnk@google.com