Correct path to tag format unit tests and child count.

- Both EndTagNoEndBrace and EndTagNoBackSlashNoEndBrace had incorrect file paths with an
extra .vtt extension i.e. .vtt.vtt. The latter also had an incorrect child count of 3
in one of it's assertions.
- I've also removed PlTagFormat from the known fails and valgrind fails as it is passing
all green now.