change default egamma calo propagator to RungeKutta ATLASRECTS-5025 (part II)
In order to increase performance for egamma, since we don't share the extrapolation to the calo any more, switch to Runge Kutta propagator, or STEP with no material effects in the calo (since a shower prb does not look as a MIP anyhow)
Tagging @christos.
Edited by Christos Anastopoulos