Description

I6_Grouping - Grouping_with_variable_sized_items changing the 'ItemSizingStrategy' also changes the header size.

Affected Test Case:
I6 - Grouping with variable sized items for Vertical list with DataTemplates.

Steps to Reproduce

1. Deploy https://github.com/dotnet/maui/tree/main/src/Controls/tests/ManualTests on iOS platform.
2. Go to I - Collection View > I6 - Grouping > I6 - Grouping with variable sized items
3. Change the ItemSizingStrategy from MeasureAllItems to MeasureFirstItem
4. Notice that the header also changes along with the images.

Actual Behavior:
Header also changes along with the images.

Expected Behavior:
Header shouldn't change even after changing the ItemSizingStrategy value.

Link to public reproduction project repository

https://github.com/dotnet/maui/tree/main/src/Controls/tests/ManualTests

Version with bug

Microsoft.Maui.Controls 10.0.20

Is this a regression from previous behavior?

Yes, this is a regression. The issue does not repro on 10.0.11 & 10.0.10.

Affected platforms

iOS