fix: drop additionalProperties: false

Unfortunately this does not mix well with
the conditional "year" property.

Author: jennifer-richards

ietf/api/views.py

@@ -529,7 +529,6 @@ def active_email_list(request):
             },
         },
         "required": ["dest", "message"],
-        "additionalProperties": False,
         "if": {
             # If dest == "nomcom-feedback"...
             "properties": {