fix: Fix BooleanField

Author: last-partizan

django_mongoengine/fields/djangoflavor.py

@@ -228,11 +228,6 @@ def formfield(self, **kwargs):
 
 
 class BooleanField(DjangoField):
-    def __init__(self, *args, **kwargs):
-        kwargs["blank"] = True
-
-        super().__init__(*args, **kwargs)
-
     def formfield(self, **kwargs):
         # Unlike most fields, BooleanField figures out include_blank from
         # self.null instead of self.blank.