DecisionHandling: Missing #include.

Add missing #include of cstdint. Fixes compilation with gcc10.

This merge request affects 1 package:

• Trigger/TrigSteer/DecisionHandling

Adding @tamartin as watcher

added Trigger master review-pending-level-1 labels

CI Result SUCCESS (hash b0d62145)

	Athena	AthSimulation
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
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 10557]

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

merged

mentioned in commit df24885f

added sweep:ignore label