Removing the GetById from IRepository

- removed it and updated everywhere, where it was called to use the async version

src/ApplicationCore/Interfaces/IRepository.cs

@@ -5,7 +5,6 @@ namespace Microsoft.eShopWeb.ApplicationCore.Interfaces
 {
     public interface IRepository<T> where T : BaseEntity
     {
-        T GetById(int id);
         T GetSingleBySpec(ISpecification<T> spec);
         IEnumerable<T> ListAll();
         IEnumerable<T> List(ISpecification<T> spec);