Update part6d.md - Clarify phrasing

This may be a bit subjective, but the unchanged version saying "on the other hand" makes it sound like the previous sentence was referring to "custom hooks" as a separate thing from the "Custom Hooks" in the following sentence.

Author: nikogenix

src/content/6/en/part6d.md

@@ -750,7 +750,7 @@ The solution is quite elegant. The entire state of the application, i.e. the val
 
 The final code for the application is in [GitHub](https://github.com/fullstack-hy2020/hook-counter/tree/part6-3) in the branch <i>part6-3</i>.
 
-As a technical detail, it should be noted that the helper functions <i>useCounterValue</i> and <i>useCounterDispatch</i> are defined as [custom hooks](https://reactjs.org/docs/hooks-custom.html), because calling the hook function <i>useContext</i> is [possible](https://reactjs.org/docs/hooks -rules.html) only from React components or custom hooks. Custom Hooks, on the other hand, are JavaScript functions whose name must start with the string _use_. We will return to custom hooks in a little more detail in [part 7](/en/part7/custom_hooks) of the course.
+As a technical detail, it should be noted that the helper functions <i>useCounterValue</i> and <i>useCounterDispatch</i> are defined as [custom hooks](https://reactjs.org/docs/hooks-custom.html), because calling the hook function <i>useContext</i> is [possible](https://reactjs.org/docs/hooks -rules.html) only from React components or custom hooks. Custom hooks are JavaScript functions whose name must start with the string _use_. We will return to custom hooks in a little more detail in [part 7](/en/part7/custom_hooks) of the course.
 
 </div>