src/test/run-pass/html-literals.rs is ignored

[alexcrichton]

With the new macro rules (#20563) this test had to be ignored.

[alexcrichton]

cc @cmr

[emberian]

If this is fixed at all, it will be by integrating detailed FIRST sets into the check, but I'm not sure we want to support something like this with macro_rules (I know @nikomatsakis has opinions about this).