Update setup.mdx

Grammar

Author: rbatsenko

docs/svelte-testing-library/setup.mdx

@@ -11,7 +11,7 @@ library with any testing framework and runner you're comfortable with.
 
 1. Install Vitest and jsdom
 
-We're using `jdom` here as the test environment, but you can use any other
+We're using `jsdom` here as the test environment, but you can use any other
 options e.g `happy-dom`.
 
 ```bash npm2yarn