Remove position-sticky test that isn't agreed upon

[stephenmcgruer]

position-sticky-input-box-gets-focused-after-scroll.html tests
behaviour that isn't widely agreed upon, as I understand it. The
test passes in Chrome only due to an unshipped feature behind
the --experimental-web-platform-features flag, which Chrome
doesn't currently intend to ship either.

[stephenmcgruer]

@flackr - can you confirm that this test should be removed? Also, is there an issue I could link to covering it?

[flackr]

Sure, removing it from compat-2021 makes sense. The behavior is agreed upon in spec but not actually shipped by any browser.

[foolip]

@flackr can you point to the spec behavior and the runtime feature that covers this? Do you know if any other browser intends to ship this anytime soon? Will it even be safe to ship (for site compat) if it happens far in the future?

[dholbert]

wpt.fyi link, for convenience: https://wpt.fyi/results/css/css-position/sticky/position-sticky-input-box-gets-focused-after-scroll.html

This test is in a section of the txt file that says # The following tests pass on all three browsers, here, though per WPT.fyi that doesn't seem to be true in this particular case.

Given that Safari, Firefox, and Chrome-in-its-shipping-configuration all fail the test with what seems to be the exact same issue[1], it makes sense to remove this from the compat2021 test set. (Rationale: to the extent that there do exist any webcompat demands around this test's behavior, they would surely be for the interoperably-shipping behavior that causes the test-failure, rather than for the test's expected behavior that nobody ships at the moment).

[1] The test failure in all browsers (including default-configured Chrome) is: Focusing on visible sticky input box should reset the scroll to unshifted sticky position. / expected 0 but got 100