[Uno] Remove Rns workaround

Talked to Jerome. This is a known Uno issue (see https://github.com/unoplatform/uno/issues/8750).

For now, we can just modify the default namespace in the csproj file? @Arlodotexe I think that'll be the simplest temporary solution.

> Working great on the linux build. I just appended `Rns` for now in the ProjectTemplate so new experiments will work as well.

Changing it for now should be fine as we're authoring the experiments, but it'd mean that VS would try and use it as the default namespace in new files which would break this pattern (though folders always make this problematic sometimes anyway for certain things).

_Originally posted by @michael-hawker in https://github.com/CommunityToolkit/Labs-Windows/issues/110#issuecomment-1124247914_