Fix vulnerability comment delete button spinner position

What does this MR do?

When viewing the vulnerability details for a vulnerability on the security dashboard:

If there's a comment on a history item at the bottom, a delete button is shown to delete the comment. Clicking on the button shows two confirmation buttons:

And when the delete button is clicked, a loading spinner is shown on the button, but is positioned incorrectly. This MR fixes that:

Before	After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

ee/app/assets/javascripts/vulnerabilities/components/history_comment.vue

 <script>
 /* eslint-disable vue/no-v-html */
-import { GlDeprecatedButton, GlButton, GlLoadingIcon } from '@gitlab/ui';
+import { GlDeprecatedButton, GlButton } from '@gitlab/ui';
 import EventItem from 'ee/vue_shared/security_reports/components/event_item.vue';
 import { deprecatedCreateFlash as createFlash } from '~/flash';
 import { __, s__ } from '~/locale';
@@ -13,7 +13,6 @@ export default {
     GlButton,
     EventItem,
     HistoryCommentEditor,
-    GlLoadingIcon,
   },
 
   props: {