Fix storage-access-api/requestStorageAccess-cross-origin-iframe-navigation-relax.sub.https.window.html to adhere to the specification

[cfredric]

Test List

https://wpt.fyi/results/storage-access-api/requestStorageAccess-cross-origin-iframe-navigation-relax.sub.https.window.html?label=master&label=experimental&aligned&q=storage-access

Rationale

This test was (tentatively?) added in relation to privacycg/storage-access#197, but in that issue we reached consensus on handling it a different way (namely via the Storage Access Headers feature). So, this test makes assertions that are not actually required by spec.

Specifically, the "Same-site-initiated same-origin navigations preserve storage access" subtest is incorrect. A minimal fix would be to change the three assert_true calls to assert_false.

[nairnandu]

@jgraham @nt1m could you please review for Gecko and WebKit respectively?

[jgraham]

This seems OK to us