🐛 Date & Time pickers black text in dark mode

[henry2man]

Describe the bug

Date & Time pickers displays text in black in dark mode when a value is selected.

To Reproduce
Steps to reproduce the behavior:

1. Go to Example app
2. Click on DatePickers or TimePickers
3. Select one value
4. Toggle Dark Mode
5. See error

Expected behavior
The text displays in white, as the placeholder does

Screenshots

Additional context
N/a

[henry2man]

@bdlukaa This can be marked as a "Good First Issue"

[henry2man]

Related to #415, I guess...