`MappingProxyType[A, B]` rendered as `MappingProxyType`

Describe the bug

Hello,

I'm not at all sure where I should open this issue, but I think sphinx might be the right place.

When documenting a propery with .. autoproperty::, look at the two cases below.

How to Reproduce

With dict: no problem

@property
def myproperty(self) -> dict[str, int]:
    ...

renders as

With MappingProxyType: problem

@property
def myproperty(self) -> MappingProxyType[str, int]:
    ...

renders as

I would expect MappingProxyType[str, int] render.

Environment Information

Created using [Sphinx](https://www.sphinx-doc.org/) 8.2.3
Built with the [PyData Sphinx Theme](https://pydata-sphinx-theme.readthedocs.io/en/stable/index.html) 0.16.1.
Using python 3.13
Ubuntu 22.04

Sphinx extensions

extensions = [
    "sphinx.ext.autosummary",
    "sphinx.ext.napoleon",
    "sphinx.ext.viewcode",
    "sphinxcontrib.bibtex",
]

├── sphinx v8.2.3 (group: dev) (*)
└── sphinxcontrib-bibtex v2.6.4a1 (group: dev) (*)

Additional context

No response

Reproduce the issue with Sphinx 8.2.3 using .. autoproperty:: and the MappingProxyType[str, int] annotation, comparing it with dict[str, int]. Start by tracing Sphinx's autoproperty type-annotation rendering; done means the rendered documentation preserves the MappingProxyType generic arguments.