Fix unit tests for BoolToObjectConverter
Fix unit tests for BoolToObjectConverter

`Test_ConvertBackRefTypeWithTypeConversion` was wrong since it expected
`TrueValue` to be converted to `false`, but it obviously should be
converted to `true`.

Although it is not used, the `targetType` expected by this method is
`bool` or something assignable from `bool`, so the tests now use that.

bkaankose/UWPCommunityToolkit,bkaankose/UWPCommunityToolkit