docs(tutorial): typo fix commandx -> command

Author: case

docs/content/tutorial/the_end.ngdoc

@@ -3,7 +3,7 @@
 @description
 
 Our application is now complete. Feel free to experiment with the code further, and jump back to
-previous steps using the `git checkout` commandx.
+previous steps using the `git checkout` command.
 
 For more details and examples of the Angular concepts we touched on in this tutorial, see the
 {@link guide/ Developer Guide}.