Revert "Pin treebeard dependency to <4.5" (#3935)

* Revert "Pin treebeard dependency to <4.5"

This reverts commit e37df74d77.

* Fix bug with dashboard redirect when upgrading to treebeard>=4.5

setup.py

     # Search support
     'django-haystack>=3.0b1',
     # Treebeard is used for categories
-    'django-treebeard>=4.3,<4.5',
+    'django-treebeard>=4.3.0',
     # Babel is used for currency formatting
     'Babel>=1.0,<3.0',
     # For manipulating search URLs

src/oscar/apps/dashboard/catalogue/views.py

 class CategoryListMixin(object):
 
     def get_success_url(self):
-        parent = self.object.get_parent()
+        parent = self.object.get_parent(update=True)
         if parent is None:
             return reverse("dashboard:catalogue-category-list")
         else: