Remove support for subpixel antialiasing and linear glyph mask backing store
Pull request: https://github.com/WebKit/WebKit/pull/5993
Committed 256201@main (797a2b50500a): <https://commits.webkit.org/256201@main> Reviewed commits have been landed. Closing PR #5993 and removing active labels.
<rdar://problem/101829604>