Fix video test flakiness from HLS cookie leakage

Clear hlsPlayback cookie before video_m3u8 tests to ensure consistent
state regardless of test execution order. The Space tests set this
cookie which can persist and break video tests when they run after.

tests/test_tweet_media.py

@@ -90,6 +90,8 @@ class MediaTest(BaseTestCase):
     @parameterized.expand(video_m3u8)
     def test_video_m3u8(self, tweet, thumb):
         self.open_nitter(tweet)
+        self.driver.delete_cookie("hlsPlayback")
+        self.refresh()
         self.assert_element_visible('.main-tweet ' + Media.container)
         self.assert_element_visible('.main-tweet ' + Media.video)