Remove obsolete FastCaloSim code

The code under Simulation/FastShower/FastCaloSim/src/obsolete has not been used for some time and is definitely safe to remove now.

FYI @schaarsc, @ahasib, @schae, @averbyts

This merge request affects 1 package:

• Simulation/FastShower/FastCaloSim

Adding @jchapman ,@vpascuzz as watchers

added Simulation master review-pending-level-1 labels

CI Result FAILURE (hash 7e256e9a)

	Athena	AthSimulation	AnalysisBase	AthGeneration
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 17489]

Failures are not related. approving - L1

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit eafa2d62

added sweep:ignore label