remove the help text about billing entity being read only

The issue is that when obj.has_inherited_billing_entity is True, the code adds
"billing_entity" to the readonly fields.

When a field is marked as readonly, Django may exclude it from form.base_fields,
which causes a KeyError when trying to access it.

src/servala/core/admin.py

@@ -73,16 +73,6 @@ class OrganizationAdmin(admin.ModelAdmin):
 
         return readonly_fields
 
-    def get_form(self, request, obj=None, **kwargs):
-        form = super().get_form(request, obj, **kwargs)
-
-        if obj and obj.has_inherited_billing_entity:
-            form.base_fields["billing_entity"].help_text = _(
-                "This billing entity is inherited from the organization's origin and cannot be modified."
-            )
-
-        return form
-
 
 @admin.register(BillingEntity)
 class BillingEntityAdmin(admin.ModelAdmin):