Add ART's Bug Component ID to `OWNERS` file.

As per go/xts-owners-policy.

Test: Rely on TreeHugger/AyeAye
Change-Id: I5de6c6059fa8dfff3d140db992a33423ca050d3c
diff --git a/OWNERS b/OWNERS
index f9f6035..06c7d08 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,3 +1,4 @@
+# Bug component: 86431
 dsrbecky@google.com
 hboehm@google.com
 jiakaiz@google.com