Delete obsolete function and object in L2MuonSA

A member function prepareRobRequests of L2MuonSA is not used in Run3 nor Run2 trigger. This doesn't need to be kept in legacy code, so can be deleted from master. m_regionSelector can be also deleted since it's only used in prepareRobRequests. Discussion can be found on ATR-22477.

ping @nakahama and @cdiez

added Trigger master labels

changed the description

This merge request affects 1 package:

• Trigger/TrigAlgorithms/TrigL2MuonSA

This merge request affects 2 files:

• Trigger/TrigAlgorithms/TrigL2MuonSA/src/MuFastSteering.cxx
• Trigger/TrigAlgorithms/TrigL2MuonSA/src/MuFastSteering.h

added review-pending-level-1 label

CI Result SUCCESS (hash da3c3d25)

	Athena	AthSimulation	AthGeneration	AnalysisBase
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
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 25319]

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

merged

mentioned in commit 022a08ba

added sweep:ignore label