style: Updated CONTRIBUTING.md

* removed the repetition of "being able to build"

CONTRIBUTING.md

@@ -21,7 +21,7 @@ These packages are described in the root file called `metadata.js` and it is pos
 
 ## Running the editor from source
 
-You need to have all the build setup of being able to build VS Code to be able to build the Monaco Editor.
+You need to have all the build setup of VS Code to be able to build the Monaco Editor.
 
 * Install all the prerequisites: https://github.com/Microsoft/vscode/wiki/How-to-Contribute#installing-prerequisites