DEV: Remove cache option from ajax() (#13142)

1. It defaults to `cache: true` already
2. Setting it to `false` for non-GET request doesn't do anything
3. We were correcting `cache: false` GET requests to use `cache: true`

…so setting it to anything at all, for any type of request doesn't make sense (anymore)

app/assets/javascripts/admin/addon/components/admin-report.js

@@ -366,7 +366,7 @@ export default Component.extend({
   },
 
   _buildPayload(facets) {
-    let payload = { data: { cache: true, facets } };
+    let payload = { data: { facets } };
 
     if (this.startDate) {
       payload.data.start_date = moment(this.startDate)