Fix dimuon mass hypo on DiMuonNoIPLine monitoring

This was supposed to be a change part of !1559 (merged) but then after rebasing the commit got lost.

It only changes the histogramming part of the code so no changes are expected in the references.

changed target branch from master to 2024-patches

@cagapopo this was part of the MR you just merged !1559 (merged) but aftert the rebase it got lost. It won't need any refupdate or anything like that. Can we add to be merged for the milestone? Sorry for the hassle.

changed title from Fix dimuon mass hypo to Fix dimuon mass hypo on DiMuonNoIPLine monitoring

changed the description

added RTA label

@kaaricha fyi

mentioned in commit 3729ffe3

merged

mentioned in merge request !1591 (merged)

mentioned in issue Moore#767 (closed)