Give the QED interaction spec the size of the QED event pool

This fixes a problem in the QED specification handed to the collision context
tool.

- The MC number string was 10000000:NEventsQED, so the round robin wrapped the
  QED event IDs at 10000000 instead of at the number of events the workflow
  simulates, and the MC labels named QED events which do not exist.
- Both numbers are NEventsQED now, which also repairs the labels on the O2
  versions already deployed.

https://its.cern.ch/jira/browse/O2-7132

Author: sawenzel

MC/bin/o2dpg_sim_workflow.py

@@ -659,7 +659,11 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True, runcommand=True):
       includeQED = False
    else:
       qedrate = INTRATE * QEDXSecExpected[COLTYPE] / XSecSys[COLTYPE]   # hadronic interaction rate * cross_section_ratio
-      qedspec = 'qed' + ',' + str(qedrate) + ',10000000:' + str(NEventsQED)
+      # the QED events are reused in a round robin, so both numbers are the size of the QED pool.
+      # Older O2 versions wrap the QED event IDs at the first number instead of the second one and
+      # would otherwise put event IDs into the MC labels which are not in the QED kinematics.
+      # See https://its.cern.ch/jira/browse/O2-7132
+      qedspec = 'qed' + ',' + str(qedrate) + ',' + str(NEventsQED) + ':' + str(NEventsQED)
 
 PreCollContextTask['cmd'] = task_finalizer([
       '${O2_ROOT}/bin/o2-steer-colcontexttool',