NFS: Don't specify NFS version in "UDP not supported" error

UDP was originally disabled in 6da1a034 for NFSv4. Later in
b24ee6c6 UDP is by default disabled by NFS_DISABLE_UDP_SUPPORT=y for
all NFS versions. Therefore remove v4 from error message.

Fixes: b24ee6c6 ("NFS: allow deprecation of NFS UDP protocol")

Signed-off-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>