[UIK-5882][theme] update value for bars

[j-mnizhek]

Changelog

@semcore/theme

Fixed

• Values for progress-bar and chart-base-bg variables became darker.

@semcore/progress-bar

Fixed

• Base background became darker.

@semcore/mini-chart

Fixed

• Base background for Score Line and Donut became darker.

@semcore/slider

Fixed

• Base background became darker.

Motivation and Context

The base color of the different bars lost its contrast against the page-bg. Just updated their value's reference from L_BG_LIGHT to L_BG_MEDIUM.

Before:

After the fix:

How has this been tested?

Manually.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Nice improve.

Checklist:

• I have updated the documentation accordingly.
• I have added new tests on added of fixed functionality.