Simplify WebVTT snap-to-line test by avoiding cue alignment settings

[foolip]

The test passes in Firefox before and after these changes. The rendering
isn't affected because these settings are the defaults.

[silviapfeiffer]

Is there another check for the passing of these settings?

[foolip]

@silviapfeiffer you can see the before/after for Firefox here:
https://wpt.fyi/results/webvtt/rendering/cues-with-video/processing-model/snap-to-line.html?diff&filter=ADC&run_id=5152780360876032&run_id=5113678978613248

And these are the after results for Chrome+Firefox+Safari, Chrome+Safari still failing:
https://wpt.fyi/results/webvtt/rendering/cues-with-video/processing-model?label=pr_head&max-count=1&pr=46455

[foolip]

A bit of context for this is that I was working on mapping the tests to the features in https://webstatus.dev/?q=webvtt and web-platform-dx/web-features#1121 which I'm adding. Looking for rendering tests for cue alignment settings I could only find this one, but it's not really a test for that. In the end, mapping the tests to features is easier if all of the tests in this directory are for the base WebVTT feature.

[silviapfeiffer]

Thanks for that clarification. Great to see you are adding specific tests for the line-left and start settings and will be testing these separately. Given this addition of tests, I'm fine with this change.

[foolip]

@silviapfeiffer to make sure there's no miscommunication, web-platform-dx/web-features#1121 is adding the feature to web-features, and I will find the tests for cue alignment settings in WPT so that they can be shown on wpt.fyi using feature:webvtt-cue-alignment. Unfortunately, there are no rendering tests for cue alignment, not even the test I'm updating here really tested it, it was just there in the syntax.

Without rendering tests the feature isn't really tested well enough. I can file an issue about this, but am not planning to improve the test coverage myself.

[silviapfeiffer]

At minimum, this test was testing the parsing of that feature, even if it didn't do a rendering test.
I understood you were adding additional tests, sorry for the misunderstanding.
Please file the issue.
If you happen to find the time to write the additional tests, that would be amazing.