Move OWNERS.rust to rust/OWNERS.

The previous attempted fix did not work on the AOSP gerrit.

Bug: none
Test: Check the suggested owners on a minijail/rust CL.
Change-Id: Idcccf70ce1057401efe23d94691c47d011d0165b
diff --git a/OWNERS b/OWNERS
index 9615a27..ebadeca 100644
--- a/OWNERS
+++ b/OWNERS
@@ -3,5 +3,3 @@
 [email protected]
 [email protected]
 [email protected]
-
-per-file rust/** = file:/OWNERS.rust
diff --git a/OWNERS.rust b/rust/OWNERS
similarity index 100%
rename from OWNERS.rust
rename to rust/OWNERS