ui5-date-picker: Text color contrast issues in High contrast black on white theme

[GongRichard]

Describe the bug
Text color contrast issues in High contrast black on white theme.

To reproduce
Steps to reproduce the behavior:

1. Go to https://github.wdf.sap.corp/pages/xweb/goalmanagementx/app.html?mock&sap-ui-theme=sap_belize_hcb#/goal-list
2. click 'Skip Tour' button
3. click more actions button on the top right of Goal Card
4. click 'Create Activity' button
5. select a new satus 'low'
6. open date picker for 'Achieved On'

Actual Results
The visual pink color ((#e269C9)) outline around the current date fails to meet 7:1 against the grey color background (#171717) and (#2E2E2E) of calendar widget.

Expected behavior
In high contrast themes, visual selected outline should meet 7:1 against their backgrounds. Hence modify the colors to meet this contrast ratio

Screenshots

Context

• UI5 Web Components version：0.23.2
• OS/Platform: {...}
• Browser (if relevant): {...}
• Other information: {...}

[ilhan007]

FYI @SAP/ui5-webcomponents-topic-b