ParticleJetTools: Fix cppcheck 2.14 warnings.

Prefer returning const references to members rather than copies.

This merge request affects 1 package:

• PhysicsAnalysis/AnalysisCommon/ParticleJetTools

This merge request affects 1 file:

• PhysicsAnalysis/AnalysisCommon/ParticleJetTools/ParticleJetTools/JetTruthLabelingTool.h

Adding @jveatch as watcher

added Analysis BTagging JetEtmiss analysis-review-required main review-pending-level-1 labels

CI Result SUCCESS (hash d944640f)

	Athena	AthGeneration	AnalysisBase	AthAnalysis
externals
cmake
make
tests

Full details available on this CI monitor view. Check the JIRA CI status board for known problems
Athena: 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-EL9 9617] (remote access info)

removed review-pending-level-1 label

removed analysis-review-required label

added review-approved label

merged

mentioned in commit 69aa2f54