Remove retired config variable

nnn.1

@@ -195,11 +195,6 @@ files.
     export NNN_RESTRICT_NAV_OPEN=1
 .Ed
 .Pp
-\fBNNN_RESTRICT_0B:\fR restrict opening 0-byte files due to unexpected behaviour; use \fIedit\fR or \fIopen with\fR to open the file.
-.Bd -literal
-    export NNN_RESTRICT_0B=1
-.Ed
-.Pp
 \fBNNN_TRASH:\fR trash (instead of \fIdelete\fR) files to desktop Trash.
 .Bd -literal
     export NNN_TRASH=1