Update testing.mdx (#1054)

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: trofivan

src/routes/guides/testing.mdx

@@ -18,7 +18,7 @@ Testing your Solid applications is important to inspiring confidence in your cod
 
 ### Adding testing packages
 
-The recommended testing testing framework for Solid applications is [vitest](https://vitest.dev). 
+The recommended testing framework for Solid applications is [vitest](https://vitest.dev). 
 
 To get started with vitest, install the following development dependencies: