Revert "StyledBar: Explicitly set fixed height"

Breaks multirow bar.

This reverts commit cc035a59b1b7800a651ff298842b6a1c7844b224.

Change-Id: Id0e056d9a9736c8700161f81fe9b482c26ec2259
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>