GSFTrackExtrapolator : Use unordered set

This merge request affects 1 package:

• Tracking/TrkFitter/TrkGaussianSumFilter

Adding @amorley as watcher

added Egamma Tracking master review-pending-level-1 labels

CI Result SUCCESS (hash ccab2a48)

	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 17836]

The changes are fine and the CI issue is unrelated. Approving.

Jason (L1)

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

merged

mentioned in commit d6478f40

added sweep:ignore label