TrkLinks: Fix gcc9 warnings.

In C++11, implicit declarations of copy and assignment are deprecated if the class has a user defined destructor or copy or assignment. gcc9 now warns about this by default. Adjust to avoid the warning.

This merge request affects 1 package:

• Tracking/TrkEvent/TrkLinks

added Tracking master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-20488-2019-01-21-23-37
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
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merged

mentioned in commit 9c099aa8

added sweep:ignore label