gh-88965: typing: fix type substitution of a list of types after initial `ParamSpec` substitution (GH-102808)

Previously, this used to fail:

```py
from typing import *
T = TypeVar("T")
P = ParamSpec("P")

class X(Generic[P]):
    f: Callable[P, int]

Y = X[[int, T]]
Z = Y[str]
```

(cherry picked from commit adb0621652f489033b9db8d3949564c9fe545c1d)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>