Problem with integration of fake rate axes with pseudodata

[cippy]

Reference line: https://github.com/WMass/WRemnants/blob/main/wremnants/CardTool.py#L643

This might be problematic when the histogram to form pseudodata has some special axes to store multiple variations (usually a categorical axis), which can't be integrated. This leads to a crash when processing the fakes. It seems to be related to the fact that the axes which are not eta-pt-charge (or others that can be specified) are integrated out to derive the fake rate, because of the invalid broadcasting of histograms with inconsistent shapes