ksmbd: remove the leftover of smb2.0 dialect support

mainline inclusion
from mainline-5.15-rc5
commit 51a13873
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I60T7G
CVE: NA

Reference: https://git.kernel.org/torvalds/linux/c/51a1387393d9



-------------------------------

Although ksmbd doesn't send SMB2.0 support in supported dialect list of smb
negotiate response, There is the leftover of smb2.0 dialect.
This patch remove it not to support SMB2.0 in ksmbd.

Cc: Tom Talpey <tom@talpey.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Böhme <slow@samba.org>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>