24-macros contains two tests which can be made to pass with the same modification

Commit 809af93, intended to "Focus the problem and clean up naming in macros", modified [two koans](https://github.com/functional-koans/clojure-koans/commit/809af93e354e5ea53c668f37dd0f249f771c9700#diff-0cae30f3f669ce93ea6b4f438959f2c522f14cbad3a38bf7a90eaeabe31b0386R38-R42) surrounding the macro now named `infix-concise`. The format of these koans was changed from "complete test and macro" to "complete macro only".

Both tests can now be made to pass with the same modification to complete `infix-concise`. In fact, it might be quite challenging to solve the first of the two while leaving the second unsolved and prompting in the terminal.

This introduces some likelihood that students completing the koans will overlook the koan, which of course is less desirable because it sets the stage for the following final code in the group.