This is an issue well known by the Mockito community, but prone to not
be fixed:
mockito/mockito#1531

Generics allow to ensure type-safety at compile time instead of runtime.
However, here it is used mainly to auto-cast the created object, thus
avoiding this burden on the developer. Indeed, it is in a context where
type safety is usually not a requirement, since the use of this method
is often the most trivial we can have: provide a class and expect a very
instance of this class in return.

This commit thus creates a less constrained mock method which builds on
Mockito's one, but without the constraint inducing this warning.