iOS.Grid : Issue with FlexGrid Theme Adaptation

[am-kh]

Issue Description:

I'm encountering an issue with the FlexGrid control in iOS when switching between dark and light themes. The FlexGrid does not appear to adapt to the new theme, and it remains fixed with a single contrast.

Steps to Reproduce:

1. Set the theme to dark mode.
2. Observe the FlexGrid appearance.
3. Change the theme to light mode.
4. Observe that the FlexGrid does not adjust to the new theme.

Expected Behavior:

I expect the FlexGrid to adapt to the current theme (dark or light) to ensure a consistent and visually appealing user experience.

Any guidance or suggestions for resolving this issue would be greatly appreciated.

Thank you for your assistance in advance.

[IrinaPykhova]

@arivoir please take a look