Too little contrast in progress indicator of inactive tab in light theme

### Windows Terminal version

1.20.11381.0

### Windows build number

10.0.19045.4529

### Other Software

_No response_

### Steps to reproduce

Configure the terminal to use the light theme (not legacy), and a tab bar separate from the title bar.
Open a PowerShell tab and run a command to output the OSC that sets 50% progress: ``"`e]9;4;1;50`e\"``
Do the same in another tab.

### Expected Behavior

The progress indicators in the tab bar should have good contrast so that I can see how much progress has been made.

### Actual Behavior

The progress indicator of the inactive tab is too light and doesn't have enough contrast to the light background:

Compare to the dark theme, where both progress indicators have adequate contrast:

No source file, test, or entry point is named. Reproduce the issue with the light theme, a separate tab bar, two PowerShell tabs, and the provided OSC progress command, then trace the tab-bar progress indicator implementation. Done means the inactive indicator has sufficient contrast against the light background while preserving the dark-theme behavior.

Written by the indexing model from the issue text.