Remove default required & strip from FullNameFormMixin

These values are the default, let’s use them.

itou/www/signup/forms.py

@@ -61,15 +61,11 @@ class FullnameFormMixin(forms.Form):
     first_name = forms.CharField(
         label="Prénom",
         max_length=User._meta.get_field("first_name").max_length,
-        required=True,
-        strip=True,
     )
 
     last_name = forms.CharField(
         label="Nom",
         max_length=User._meta.get_field("last_name").max_length,
-        required=True,
-        strip=True,
     )