Add vapier@ to OWNERS.

Mike has been reviewing a bunch of Minijail CLs, and has good insights
as to how folks use the tool.

Bug: None
Test: None
Change-Id: Id3e734537446b373cba9b1e5d4f4e9c9bccaaff9
diff --git a/OWNERS b/OWNERS
index ec6db46..ebadeca 100644
--- a/OWNERS
+++ b/OWNERS
@@ -2,3 +2,4 @@
 [email protected]
 [email protected]
 [email protected]
[email protected]