docs: fix typo for preact-api docs (testing-library#690)

Author: denis-tsoi-mox

docs/preact-testing-library/api.mdx

@@ -77,7 +77,7 @@ responsible for flushing all effects and rerenders after invoking it.
 
 📝 If you'd love to learn more, checkout
 [this explanation](https://github.com/threepointone/react-act-examples/blob/master/sync.md).
-Even thought it's for React, it gives you an idea of why it's needed.
+Even though it's for React, it gives you an idea of why it's needed.
 
 ## `fireEvent`