Update admin page by removing download feature

[kylos101]

[gtsiolis]

This seemed trivial to fix and opened #14393 to removing the user-facing button to download the workspace.

The PR does not remove any backend services or endpoints, as downloading workspaces from the dashboard is still being used, see #14381. Cc @kylos101 @atduarte

[gtsiolis]

Closing this as it was resolved in #14393.

[gtsiolis]

Validating this works in production.