Update CHANGELOG.md

CHANGELOG.md

@@ -17,7 +17,7 @@
 * `RichardsSimulation` now has its own `RichardsSimulationTraits` derived from
     `BaseTraits`, which defines all its member types. `BaseTraits` now have
     reduced content and are intended to be shared between models/simulations.
-* The test system folder was renamed from testing to [test](test).
+* The test system folder was renamed from `testing` to [`test`](test).
 
 ### Fixed
 * Removed VTK output from `dorie_mass_conservation` executable, which would