Fix styling of th elements when explicitly specifiying text-align:inherit https://bugs.webkit.org/show_bug.cgi?id=138577 Patch by Ryan Reno <rreno@apple.com> on 2022-06-16 Reviewed by Tim Nguyen. <th> elements were being incorrectly centered when specifying text-align: inherit. This fixes that bug by adding a new internal CSS value for use in the UA stylesheet. This also removes a non-inherited