ui: make tree settings button like regular buttons

ui: make tree settings button like regular buttons

the "proxmox-inline-button" class is redundant in the crisp theme as
it only sets the buttons text to black. we mainly use that class for
"help" buttons. this is useful in the dark theme, because we want help
buttons to stand out a bit so (possibly confused) users are drawn to
them more easily. removing the class here doesn't change anything for
"crisp", but makes the dark theme appear more consistent. also fixes
up an unnecessary space.

Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>