Increase the debounce of Issue Suggestions

This increases the debounce for issue suggestions requests to `1000ms`.
This is to reduce the number of requests that we send.

app/assets/javascripts/issuable_suggestions/components/app.vue

@@ -27,7 +27,7 @@ export default {
   apollo: {
     issues: {
       query,
-      debounce: 250,
+      debounce: 1000,
       skip() {
         return this.isSearchEmpty;
       },