make sure to weight the histograms by the event weight

this does not affect the distribution shapes greatly since the weights
are extremely close to exactly 1/B within each sample

DQM/src/DQM/DarkBremInteraction.cxx

@@ -195,6 +195,7 @@ void DarkBremInteraction::onProcessStart() {
  * and then use the electron mass to calculate its total energy.
  */
 void DarkBremInteraction::produce(framework::Event& event) {
+  histograms_.setWeight(event.getEventHeader().getWeight());
   const auto& particle_map{event.getMap<int,ldmx::SimParticle>("SimParticles")};
   const ldmx::SimParticle *recoil{nullptr}, *aprime{nullptr}, *beam{nullptr};
   for (const auto& [track_id, particle] : particle_map) {