LU-14301 lustre: add ENOTSUPP to spelling.txt

LU-14301 lustre: add ENOTSUPP to spelling.txt

Add a spelling check for ENOTSUPP to suggest use of EOPNOTSUPP
instead. Note:

ENOTSUPP (524) and defined only in the kernel errno.h and is a NFSv3
specific errno. If ENOTSUPP is returned to userspace then strerror()
will print "Unknown error 524".

EOPNOTSUPP (95) is defined in kernel and userspace errno.h.

ENOTSUP is defined in userspace errno.h as an alias for EOPNOTSUPP.

Lustre-change: https://review.whamcloud.com/41280
Lustre-commit: e00733f0f87659c936039a58ea738cfb070638bc

Test-Parameters: trivial
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I13b0389c9ec0853f43d8ab4a8f6538eb24c8a2ad
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51512
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>