Remove redundant "export" from man page

nnn.1

@@ -311,7 +311,7 @@ for filenames having quote(s) in them.
 .Pp
 \fBNNN_NO_AUTOSELECT:\fR Disable directory auto-selection in \fInavigate-as-you-type\fR mode.
 .Bd -literal
-    export export NNN_NO_AUTOSELECT=1
+    export NNN_NO_AUTOSELECT=1
 .Ed
 .Sh KNOWN ISSUES
 If you are using urxvt you might have to set backspace key to DEC.