How do I reset a rewrite?

.htaccess rules are interpreted and applied on every request, they don’t linger on server level and changes apply immediately.

However if you had had 301 redirect set up then it can be cached by browser very aggressively. I do not observe redirect you are describing, so that is likely the case.

Note that your home URL 404s for me right now, so you might have more issues than just rewrite there going on.