typing fix for mypy 1.18 (#13427)

Author: alex

src/cryptography/hazmat/bindings/openssl/binding.py

@@ -58,7 +58,7 @@ class Binding:
     OpenSSL API wrapper.
     """
 
-    lib: typing.ClassVar = None
+    lib: typing.ClassVar[typing.Any] = None
     ffi = _openssl.ffi
     _lib_loaded = False
     _init_lock = threading.Lock()