smb: server: remove code guarded by nonexistent config option

smb: server: remove code guarded by nonexistent config option

A small piece of code in fs/smb/server/smb_common.c depends on
CONFIG_SMB_INSECURE_SERVER, which has never been defined in the
mainline kernel, but was present in old out-of-tree versions of ksmbd.
Remove this dead code.

Discovered while searching for CONFIG_* symbols referenced in code but
not defined in any Kconfig file.

Signed-off-by: Ethan Nelson-Moore <enelsonmoore@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>