Add @type_check_only to stub-only private classes in various third-party stubs (#15535)

stubs/paramiko/@tests/stubtest_allowlist.txt

@@ -1 +0,0 @@
-paramiko.util.SupportsClose

stubs/paramiko/paramiko/util.pyi

@@ -3,15 +3,12 @@ from collections.abc import Iterable
 from hashlib import _Hash
 from logging import Logger, LogRecord
 from types import TracebackType
-from typing import IO, AnyStr, Protocol
+from typing import IO, AnyStr
 from typing_extensions import Self
 
 from paramiko.config import SSHConfig, SSHConfigDict
 from paramiko.hostkeys import HostKeys
 
-class SupportsClose(Protocol):
-    def close(self) -> None: ...
-
 def inflate_long(s: bytes | bytearray, always_positive: bool = False) -> int: ...
 def deflate_long(n: int, add_sign_padding: bool = True) -> bytes: ...
 def format_binary(data: bytes | bytearray, prefix: str = "") -> list[str]: ...