Remove wildcard from ART tests' OWNERS file.

This is in line with the policy to tighten ART's OWNERS file in
general (see e.g.
https://android-review.googlesource.com/c/platform/art/+/1757576/).

Test: build/make/tools/checkowners.py -c art/test/OWNERS
Bug: 193029862
Change-Id: I67b1b9a0f34228df0c06c4f1cbc65af26e09979d
diff --git a/test/OWNERS b/test/OWNERS
index 28d5064..7d11748 100644
--- a/test/OWNERS
+++ b/test/OWNERS
@@ -1,4 +1,3 @@
 # See also ART owners in the parent directory.
 rpl@google.com
 dsrbecky@google.com
-*