[Common] customize ratio plot draw option in ReferenceComparator (#2600)

By default the histograms are drawn with error bars ("E" option), however
there are cases where the user might want to hide the errors and draw
the histograms with the "H" option, for example because the error bars
are unreliable or unphysical.

This can already be done by passing a custom draw option via the task
configuration interface.
However, the customized draw option is only passed to the current and
reference histograms, but not to the ratio plot, which is always drawn
with the "E" option.
The commit extends the custom draw option also to the ratio histogram.

Author: aferrero2707

Modules/Common/src/ReferenceComparatorPlot.cxx

@@ -306,8 +306,8 @@ class ReferenceComparatorPlotImpl1D : public ReferenceComparatorPlotImpl
     }
     mRatioPlot->SetLineColor(kBlack);
     mRatioPlot->SetStats(0);
-    mRatioPlot->SetOption("E");
-    mRatioPlot->Draw("E");
+    mRatioPlot->SetOption(drawOption.c_str());
+    mRatioPlot->Draw(drawOption.c_str());
     if (drawRatioOnly) {
       mRatioPlot->SetMinimum(0);
       mRatioPlot->SetMaximum(2);