bench: remove duplicate variable declaration

PR-URL: #5159
Closes: #5144
Reviewed-by: Athan Reines <[email protected]>

Author: ekambains

lib/node_modules/@stdlib/stats/base/dists/arcsine/mean/benchmark/benchmark.js

@@ -31,7 +31,6 @@ var mean = require( './../lib' );
 // MAIN //
 
 bench( pkg, function benchmark( b ) {
-	var len;
 	var min;
 	var max;
 	var len;