Problems require iteration to solve them #1675

How should we update the material?

In the practice-tdd folder there are 2 challenges - count and repeat-str - which lend themselves to iterative solutions but at this stage of the curriculum, for loops are yet to be introduced.

These functions should be removed (possibly moved into the later module) and possibly replaced with a non-iterative problem. I say "possibly" because we may have overly stacked this sprint, so removing some tasks may be appropriate.