[requests] adapters.HTTPAdapter.close() not typed

[mharding-hpe]

With the following example code:

from requests.adapters import HTTPAdapter

class TimeoutHTTPAdapter(HTTPAdapter):
    """
    An HTTP Adapter that allows a session level timeout for both read and connect attributes.
    This prevents interruption to reads that happen as a function of time or istio resets that
    causes our applications to sit and wait forever on a half open socket.
    """

def harf(x: TimeoutHTTPAdapter | None) -> None:
    if x is not None:
        x.close()

This issue leads to the following mypy complaint:

error: Call to untyped function "close" in typed context  [no-untyped-call]

Looking at the source for requests, this method returns None, and has done so since at least version 1.0.0.

[mharding-hpe]

I have raised this PR to address this:
#15684

I do not know how backports are handled for typeshed, but because this change is valid for every version of requests back to 1.0.0, I think this would be appropriate to backport to relevant versions of types-requests