[BUG]: C++ instance passed as pointer not marked as optional in function signature

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Problem description

When passing a C++ instance as a pointer, the default behaviour is to accept None as described in the documentation. Consider the following example:

py::class_<Dog>(m, "Dog").def(py::init<>());
m.def("bark",
      [](const Dog* dog) { return dog ? "woof!" : "(no dog)"; },
      py::arg("dog")=py::none());

The function signature in help(module) looks like this:

FUNCTIONS
    bark(...) method of builtins.PyCapsule instance
        bark(dog: module.Dog = None) -> str

but we would expect this signature instead:

FUNCTIONS
    bark(...) method of builtins.PyCapsule instance
        bark(dog: Optional[module.Dog] = None) -> str

I tested with pybind11 2.7.1.

Reproducible example code

No response

Start with the documented allow/prohibiting None behavior and reproduce the supplied m.def("bark", ...) example, then inspect how help(module) renders the pointer argument in the function signature. Done means the signature shows Optional[module.Dog] for the nullable pointer while preserving the default None behavior.