Resolve "substitution planning "cancelled" checkbox does not have false as value when unchecked actively"

Closes #241 (closed)

aleksis/apps/chronos/frontend/components/AmendLesson.vue

@@ -166,7 +166,7 @@ export default {
       };
     },
     transformPatchData(item) {
-      let { id, __typename, cancelled, ...patchItem } = item;
+      let { __typename, cancelled, ...patchItem } = item;
       return {
         ...patchItem,
         // Normalize cancelled, v-checkbox returns null & does not