Pipeline Graph Drodpown: Use fluidWidth

To make it easier to identify long job items, we set
fluidWidth to true to enable a wider view.

Changelog: changed

app/assets/javascripts/ci/pipeline_details/graph/components/job_group_dropdown.vue

@@ -74,6 +74,7 @@ export default {
     :id="computedJobId"
     class="ci-job-group-dropdown"
     block
+    fluid-width
     placement="right-start"
     data-testid="job-dropdown-container"
   >