docs(tutorial): fix grammar

Should either be "a different version" or "different versions";
this goes with the latter.

Closes #10249

Author: erictheise

docs/content/tutorial/index.ngdoc

@@ -116,7 +116,7 @@ npm --version
 ```
 
 
-<div class="alert alert-info">If you need to run a different versions of node.js
+<div class="alert alert-info">If you need to run different versions of node.js
   in your local environment, consider installing
   <a href="https://github.com/creationix/nvm" title="Node Version Manager Github Repo link">
     Node Version Manager (nvm)