Fix for headlineSmall Font Size in OmniDateTimePicker

[binzheng]

Description:

Font Issue on iPad 10th Generation: When setting the headlineSmall property to fontSize: 34, the text appears to be cut off, especially on an iPad 10th generation. Specifically, 2-digit numbers are only displaying as a single digit, which affects the usability.

Steps to Reproduce: Set up the OmniDateTimePicker with headlineSmall set to fontSize: 34. Open the picker on an iPad 10th generation device or simulator. Notice that the numbers get cut off. Expected Behavior: All numbers, including 2-digit numbers, should display completely without getting cut off.

Actual Behavior: 2-digit numbers are getting cut off and only showing as a single digit.

Environment: Flutter version: [your_flutter_version] OmniDateTimePicker version: 1.0.8