python3Packages.sshfs.optional-dependencies.pyopenssl: fix the eval

Without the change the eval fails as:

    nix-repl> python3Packages.sshfs.optional-dependencies.pyopenssl
    error:
       … while evaluating the attribute 'sshfs.optional-dependencies.pyopenssl'
         at pkgs/development/python-modules/sshfs/default.nix:45:5:
           44|     pkcs11 = [ asyncssh ] ++ asyncssh.optional-dependencies.pkcs11;
           45|     pyopenssl = [ asyncssh ] ++ asyncssh.optional-dependencies.pyopenssl;
             |     ^
           46|   };

       … while evaluating the attribute 'optional-dependencies.pyopenssl'
         at pkgs/development/interpreters/python/mk-python-derivation.nix:229:15:
          228|     // optionalAttrs (optional-dependencies != {}) {
          229|       inherit optional-dependencies;
             |               ^
          230|     }

       error: attribute 'pyopenssl' missing
       at pkgs/development/python-modules/sshfs/default.nix:45:33:
           44|     pkcs11 = [ asyncssh ] ++ asyncssh.optional-dependencies.pkcs11;
           45|     pyopenssl = [ asyncssh ] ++ asyncssh.optional-dependencies.pyopenssl;
             |                                 ^
           46|   };