Investigate where we use `django-select2`

[Xiphoseer]

Django includes select2, but we use this random package for some reason. We should investiagate that and remove it, if we don't use it.

[joachimschmidt557]

Apparently, djangocms-cascade needs django-select2:

https://github.com/jrief/djangocms-cascade/blob/fe954059f49aa4549e5a781aa1a189f1c8a53f1d/cmsplugin_cascade/apps.py#L17