[fix] Fixed Geometry Map visibility django 5.2 #166

Django release 5.1 has removed support for handling dimensions
of geometry widget which led to geometry field not visible.
Now we are using `LeafletAdminWidget` which provides css for
dimensions of geometry widget.
Added selenium test cases for the above case to test visibility of map.

Fixes #166

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Signed-off-by: DragnEmperor <dragnemperor@gmail.com>
Co-authored-by: Federico Capoano <f.capoano@openwisp.io>
Co-authored-by: Gagan Deep <pandafy.dev@gmail.com>