nfsd4: remove obselete comment

Mandatory locking has been removed.  And the rest of this comment is
redundant with the code.
Reported-by: Jeff layton <jlayton@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

@@ -730,9 +730,6 @@ __nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
 	path.dentry = fhp->fh_dentry;
 	inode = d_inode(path.dentry);
 
-	/* Disallow write access to files with the append-only bit set
-	 * or any access when mandatory locking enabled
-	 */
 	err = nfserr_perm;
 	if (IS_APPEND(inode) && (may_flags & NFSD_MAY_WRITE))
 		goto out;