Remove extra margin above issue navigation tabs

What does this MR do?

This MR removes extra margin above the issue navigation tabs on issue lists. It fixes a regression introduced via !54893 (merged) when no JIRA issue import is occurring.

The margin is removed by hiding the jira_issues_import_status_app.vue component when it has no content. Ideally, there would be a utility class using the :empty pseudo-class to hide empty classes. I decided for a programmatic solution over a styling one because I didn't want to use a new specific class which should be a utility class.

Related to #325433 (closed)

Screenshots (strongly suggested)

Before	After

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