Tighten ART's OWNERS file.

No longer use a wildcard in OWNERS; instead, explicitly list all
ART members.

(cherry picked from commit 3362cf159a0766f4a45691f7be568a88d0e60a8a)

Test: build/make/tools/checkowners.py -c art/OWNERS
Bug: 193218514
Bug: 193029862
Change-Id: I928ab19e413c35611e9f9c97948c21af5f7b44e2
Merged-In: I928ab19e413c35611e9f9c97948c21af5f7b44e2