PanTauAlgs: Switch to using a unique_ptr instead of raw one for the TFile in PanTau::Tool_ModeDiscriminator

This would make sure we close the file after reading it and save some memory. Otherwise, ROOT caches the information and keeps it until the job quits.

Closes ATLASRECTS-6058

This merge request affects 1 package:

• Reconstruction/PanTau/PanTauAlgs

This merge request affects 1 file:

• Reconstruction/PanTau/PanTauAlgs/Root/Tool_ModeDiscriminator.cxx

Adding @goetz ,@xiaozhon ,@adbailey as watchers

added Reconstruction Tau master review-pending-level-1 labels

CI Result SUCCESS (hash b5d38525)

	Athena	AthSimulation	AthGeneration	AnalysisBase	AthAnalysis
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
AthAnalysis: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 29053]

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

merged

mentioned in commit 3f3bdec6

added sweep:ignore label