Update generic error message when submitting issues

See https://gitlab.com/gitlab-org/gitlab-ce/issues/34336

app/assets/javascripts/issuable/related_issues/components/related_issues_root.vue

@@ -119,7 +119,7 @@ export default {
           .catch((res) => {
             this.isSubmitting = false;
             // eslint-disable-next-line no-new
-            new Flash(res.data.message || 'An error occurred while submitting related issues.');
+            new Flash(res.data.message || 'We can\'t find an issue that matches what you are looking for.');
           });
       }
     },