[Clang][Comments] Parse `<img src=""/>` in doc comments correctly

This is a valid HTML5 tag. Previously it triggered a Clang error (`HTML start tag prematurely ended, expected attribute name or '>'`) since Clang was treating `/>` as a text token. This was happening because after lexing the closing quote (`"`) the lexer state was reset to "Normal" while the tag was not actually closed yet: `>` was not yet parsed at that point.

rdar://91464292

Differential Revision: https://reviews.llvm.org/D132932