Merge branch 'hsagar63/519369-fix-search-icon' into 'master'

Fix CSS: Update Dropdown Z-Index for Proper Layering

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/181676



Merged-by: Janis Altherr <jaltherr@gitlab.com>
Approved-by: Angelo Gulina <agulina@gitlab.com>
Approved-by: Janis Altherr <jaltherr@gitlab.com>
Reviewed-by: Angelo Gulina <agulina@gitlab.com>
Reviewed-by: Janis Altherr <jaltherr@gitlab.com>
Co-authored-by: Harsh Sagar <hsagar63@gmail.com>