Remove language field from submission schema

We are not updating the JSON schema for submissions. So the changes we
made to this test fixture are no longer valid.

We'll update the schema here and the one in the product pages properly
when we have a process for doing so.

Author: thomasiles

spec/fixtures/json_submission_schema_v1.json

@@ -16,10 +16,6 @@
       "type": "string",
       "format": "date-time"
     },
-    "language": {
-      "enum": ["en", "cy"],
-      "description": "The language the form was submitted. If there is a Welsh version of the form then this will be 'cy', otherwise 'en'."
-    },
     "answers": {
       "description": "An array containing all the answers provided.",
       "type": "array",