Contrast color for data label with background color set does not work

#### Expected behaviour
When `backgroundColor` is set for a `dataLabel` with `style.color: 'contrast'`, the contrast is set relative to the background color.

#### Actual behaviour
Data label color set to contrast does not apply to the background color.

#### Live demo with steps to reproduce
https://jsfiddle.net/BlackLabel/adtzoqfm/

#### Product version
Highcharts v11.1.0
