Adds a more descriptive link purpose (gatsbyjs#9266)

* Adds a more descriptive link purpose 

In line with part one, the link to the next part should use the part's name.

* Update docs/tutorial/part-two/index.md

Co-Authored-By: obeid <talal@transloc-inc.com>

* edited for an error

docs/tutorial/part-two/index.md

@@ -489,4 +489,4 @@ and more!
 
 ## What's coming next?
 
-Now continue on to [Part Three](/tutorial/part-three/) of the tutorial.
+Now continue on to [Creating nested layout components](/tutorial/part-three/), the third part of the tutorial.