Backfill OWNERS for VtsHalGraphicsMapper tests.

Done for the following tests:
VtsHalGraphicsMapperV2_0TargetTest
VtsHalGraphicsMapperV2_1TargetTest
VtsHalGraphicsMapperV3_0TargetTest
VtsHalGraphicsMapperV4_0TargetTest

Deleted the OWNERS file I created earlier to comply to your team's
convention.

Test: Tree Hugger
Bug: 143903671
Change-Id: I07790171fc1a42da37a43f590d8c5c2876ad1bfe