Fix nullability on `IDesignerSerializationProvider.GetSerializer`#81203

Merged

stephentoub merged 2 commits intodotnet:mainfrom

elachlan:IDesignerSerializationProvider-nullability

Jan 31, 2023

Commits on Jan 26, 2023

Fix nullability on IDesignerSerializationProvider.GetSerializer
elachlan
committed

Commits on Jan 27, 2023

Add nullability to ref IDesignerSerializationProvider interface
elachlan
committed