docs: update example

Signed-off-by: Athan <kgryte@gmail.com>

Author: kgryte

lib/node_modules/@stdlib/stats/base/ndarray/dnanstdevpn/README.md

@@ -164,7 +164,7 @@ var opts = {
     'dtype': 'float64'
 };
 
-var xbuf = filledarrayBy( 10, 'float64', rand );
+var xbuf = filledarrayBy( 10, opts.dtype, rand );
 var x = new ndarray( opts.dtype, xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );
 console.log( ndarray2array( x ) );