Remove test_global_styles_user_cpt_change_invalidates_cached_stylesheet

[mmtr]

Follows up #45679

What?

Removes the test_global_styles_user_cpt_change_invalidates_cached_stylesheet test that was added in #45679.

Why?

Because the test was added to check that the cached global stylesheet is cleared up after changing the Global Styles CPT. But after removing the filter that short-circuits the cache (see #45679 (comment)), the test is unable to check such behavior anymore, given that the cache is never used when test runs because WP_DEBUG is enabled.

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[felixarntz]

@mmtr Is this test causing failures in trunk?

It's of course not great to remove tests, so I want to make sure we bring this test back once we can (for example as part of #45912, since then there likely will be some filter again).

[mmtr]

@felixarntz It is not! But the test is not checking anything since it was intended for verifying that gutenberg_get_global_stylesheet wasn't returning a cached value after updating the wp_global_styles CPT. Since the cache is not used when WP_DEBUG is enabled, and given that the test environment has WP_DEBUG enabled, the test is pointless (gutenberg_get_global_stylesheet won't return a cached value ever) – hence why I opted for removing it.

I agree we should add it back as part of #45912 once we have a way for the tests to use the cache.

[oandregal]

This is unfortunate, but I don't see another way forward at the moment.