Remove broken check from QSO form

The check disallowed having a QSO with any callsign that is also a
reference. Obviously the user should also be able to log this kind
of QSO, even if it might not make sense. We don't judge.

contest/forms.py

@@ -93,8 +93,6 @@ class QSOForm(forms.ModelForm):
 
     def clean_call(self):
         data = self.cleaned_data["call"].upper().strip()
-        if Reference.objects.filter(name=data).count() > 0:
-            raise forms.ValidationError("Reference already exists")
 
         try:
             CallLogValidator()(data)