We need to add back in the time derivative to do a Transient calculation...

$$$$\rho cp \frac{\partial T}{\partial t} - \nabla \cdot k \nabla T = 0$$$$

This term already exists in the HeatConduction module it's called `HeatConductionTimeDerivative`

...

modules/heat_conduction/src/HeatConductionTimeDerivative.C

All we need to do is use it in an input file...