Updated Step.03-Exercise branch does not lead students towards updated Step.03-Solution branch

[chr-ibb]

The current state of the Step.03 branches is extremely confusing.

The Solution has been updated to use new retrofit Suspend support in place of deprecated Deferred. This solution is completely different from the one in the course video, but it's up-to-date, which may be more desirable.

The issue is that the updated Exercise branch changes some TODOs (1, 5 and 6) to help students arrive at the new solution, but leaves the rest unchanged. Aside from one TODO (7), the rest of the unchanged TODOs (2, 3, 4, and 8) instruct the students to write code that either: will not run because of the removed dependencies, or is completely unnecessary due to the changes to TODOs 5 and 6.

Additionally, updated TODOs alone are likely not enough to guide some students towards the new solution, since, for this section of the course, the video and text supplied have very little resemblance to the new solution.

Changes to remove the deprecated dependencies and update a few TODOs were merged, meaning the new solution is desired. For students to be able to arrive at the new solution reliably, I think all of the TODOs should be updated consistently and additional comments should be added concisely explaining the differences between the course video solution and the new solution.