Fix an issue where data-elses were being resolved twice, which was incorrect. Fixes #45253.
Merge pull request #45258 from jeresig/fix-45253

Fix an issue where data-elses were being resolved twice, which was incorrect. Fixes #45253.
Run clean-exercises on the HTML exercises, fixing the entities inside the data-if attributes.
Fix endlines at the ends of some files. Fix corroded entities in khan-exercise.html. Fix broken data-if expression.