Correctly unparse EQEQEQ into === (instead of ==).

Reported by Pradyoth Kukkapalli on the kotlin-students mailing list.

When I added token unparsing to the JetTokens class (626ec6519c05c5087f73c2be2fbca91eec80fc84), I mapped `EQEQEQ` to `==` instead of `===`. This won't have broken any existing code but would have caused bugs in any new code relying on this unparsing information (sorry).