Fix include syntax on libcore/OWNERS file

The syntax requires the project to be specified
as a prefix.

Change-Id: I9b7bea65d51651a116a78c877da615905c249ddb
Exempt-From-Owner-Approval: Fixes OWNERS
Test: None
diff --git a/OWNERS b/OWNERS
index 17cb81c..87a5dbe 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1 +1 @@
-include ../../libcore/OWNERS
+include platform/libcore:/OWNERS