Fix more cypress tests

client/cypress/fixtures/me.join-class.json

@@ -9,6 +9,7 @@
     "lastName": "Cueni",
     "avatarUrl": "",
     "isTeacher": false,
+    "readOnly": false,
     "lastModule": {
       "id": "TW9kdWxlTm9kZToxNw==",
       "slug": "lohn-und-budget",

client/cypress/fixtures/selected-school-class.json

@@ -2,6 +2,7 @@
   "me": {
     "id": "VXNlck5vZGU6Mg==",
     "isTeacher": false,
+    "readOnly": false,
     "selectedClass": {
       "id": "U2Nob29sQ2xhc3NOb2RlOjE=",
       "name": "Moordale",

client/cypress/integration/frontend/spellcheck.spec.js

@@ -8,6 +8,7 @@ const operations = {
     me: {
       permissions: [],
       onboardingVisited: true,
+      readOnly: false
     },
   },
   AssignmentQuery: {