Replace local timezone with UTC

[rikroe]

Proposed change

I don't think we need local timezones anymore, as we can provide UTC to the BMW API.
Should solve home-assistant/core#115243.

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (which adds functionality to this library)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:

Checklist

• The code change is tested and works locally.
• Tests have been added to verify that the new code works.