[Gecko Bug 1789081] fontstyle/fontweight attributes should not cancel automatic mathvariant transform on single-char mi.

[moz-wptsync-bot]

Some code was introduced in [1] to fix a regression with deprecated fontstyle/fontweight attributes. However, this is no longer needed since implementation for these attributes have been completely removed [2] and may prevent automatic mathvariant italicization on single-char . Also add a WPT test to check for this.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1027354 [2] https://bugzilla.mozilla.org/show_bug.cgi?id=1783841

Differential Revision: https://phabricator.services.mozilla.com/D156373

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1789081 gecko-commit: 93f99157f81e934d7f895704d10c227bf2329bd6 gecko-reviewers: emilio