bench: refactor to use string interpolation in array/base/fill-by

PR-URL: stdlib-js#8899
Ref: stdlib-js#8647
Co-authored-by: Athan Reines <kgryte@gmail.com>
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: JavaTypedScript

lib/node_modules/@stdlib/array/base/fill-by/benchmark/benchmark.length.js

@@ -24,6 +24,7 @@ var bench = require( '@stdlib/bench' );
 var pow = require( '@stdlib/math/base/special/pow' );
 var isArray = require( '@stdlib/assert/is-array' );
 var ones = require( '@stdlib/array/base/ones' );
+var format = require( '@stdlib/string/format' );
 var pkg = require( './../package.json' ).name;
 var fillBy = require( './../lib' );
 
@@ -102,7 +103,7 @@ function main() {
 		len = pow( 10, i );
 
 		f = createBenchmark( len );
-		bench( pkg+':dtype=generic,len='+len, f );
+		bench( format( '%s:dtype=generic,len=%d', pkg, len ), f );
 	}
 }