Fix date picker text color

[thomasloven]

Proposed change

The background to this is that the date and time input in a datetime entity row can look different with some themes.

That's because the date picker uses --material-body-text-color first and --primary-text-color second.

This change just makes --primary-text-color the first choice.

I'm not sure this is the right solution, as it blocks more fine-grained control...

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io