tests: Hide warning "cannot remove 'uri_playlist'"
tests: Hide warning "cannot remove 'uri_playlist'"

This file is only created by `start_fake_video_src`, not by
`start_fake_video_src_launch`, but in both cases `stop_fake_video_src`
tries to remove it.

It's only used (via `fake_video_src_show`) by
`test_that_validation_video_served_over_http_is_correct`.

LewisHaley/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester