Popover covers Export button on dependency list

Summary

There is a popover which covers the export button on the dependency list page and prevents it from being clicked.

Possible solution

Remove gl-overflow-auto from the parent <header>.

Verification steps

1. go to https://gitlab.com/groups/gitlab-org/govern/threat-insights-demos/verification-projects/-/dependencies
2. verify that when hovering the "Export" button, the tooltip does not cover the button and it's clickable
3. narrow your browser window to to about mobile size
4. verify the "Export" button is still nicely positioned (it will wrap to a new line and be left aligned) and the tooltip still does not cover the button on hover