chromium_factory: Remove 'ui_unittests' references.
chromium_factory: Remove 'ui_unittests' references.

After grepping through 'build' and 'build_internal' sources, nothing
seems to reference these tests anymore, as the active milestones where
they are valid have aged off.

BUG=chromium:434498
TEST=None

Review URL: https://codereview.chromium.org/1001033002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@294421 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build