EventDisplaysOnline: Add missing override to fix clang warnings

This MR fixes several clang build warnings in JiveXML related packages - the warning started with a sweep from 24.0 to the main branch that contained MR !67647 (merged). Therefor starting this MR also in the 24.0 branch.

Tagging @myexley and @tsulaia for info.

This merge request affects 1 package:

• graphics/EventDisplaysOnline

This merge request affects 1 file:

• graphics/EventDisplaysOnline/EventDisplaysOnline/OnlineEventDisplaysSvc.h

Adding @rbianchi as watcher

added 24.0 EventDisplay review-pending-level-1 labels

CI Result SUCCESS (hash c70d7d72)

	Athena
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
For experts only: Jenkins output [CI-MERGE-REQUEST-EL9 8421] (remote access info)

Changes look fine and the CI is good. Approving. Clara (L1)

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

added review-approved-tier0 label

merged

mentioned in commit 241f6122

mentioned in merge request !70805 (merged)