TrkAlignableSurfaces. Clang llvm 9 warnings on missing override

Mentioning @ssnyder as I know he is looking at some of these, so as we do not overlap

This merge request affects 1 file:

• Tracking/TrkDetDescr/TrkAlignableSurfaces/TrkAlignableSurfaces/AlignablePlaneSurface.h

Adding @amorley as watcher

added Tracking master review-pending-level-1 labels

CI Result SUCCESS (hash 9a7dd527)

	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 23473]

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

merged

mentioned in commit 7a80b1e5

added sweep:ignore label