Fix for failing on sectiondef description
Fix for failing on sectiondef description

Raised on the librelist. It is possible for a sectiondef element to have
a description which we already have code for displaying but it was
falling foul of the filters when :members: was being used as it is a
child of sectiondef but isn't itself a member to fall into the :members:
list.

Here we add an exception to the filter to allow it to slide through.

AnthonyTruchet/breathe,RR2DO2/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,RR2DO2/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,kirbyfan64/breathe