Unskip test for videos without PTS values

[NicolasHug]

Address this TODO:

torchcodec/test/test_decoders.py

Lines 998 to 1005 in a3867d1

	# The test video we have is from
	# https://huggingface.co/datasets/raushan-testing-hf/videos-test/blob/main/sample_video_2.avi
	# We can't check it into the repo due to potential licensing issues, so
	# we have to unconditionally skip this test.#
	# TODO: encode a video with no pts values to unskip this test. Couldn't
	# find a way to do that with FFmpeg's CLI, but this should be doable
	# once we have our own video encoder.
	pytest.skip(reason="TODO: Need video with no pts values.")