Service map page: remove unnecessary scroll

[yannikmesserli]

No issue.

Summary

No matter what, the service map page were showing a scroll on Chrome. This PR removes it.

Changes

• Remove hidden elements from DOM's tree using display: none instead of visibilitiy: hidden

Screenshots

Before	After

Functional testing

• Open Hubble UI and select a namespace
• Observe that the page does not have a scroll bar anymore on the entire body
• !!!important!!! Verify that if you move your mouse over the "lock" icons, the tooltup is still displayed:

I could not test the last part because I am not sure when those icons show up. using the default demo app, it is not showing up