docs: fix example

Signed-off-by: Athan <[email protected]>

Author: kgryte

lib/node_modules/@stdlib/stats/base/dnanmeanwd/README.md

@@ -119,7 +119,7 @@ var Float64Array = require( '@stdlib/array/float64' );
 
 var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN ] );
 
-var v = dnanmeanwd( 4, x, 2, 1 );
+var v = dnanmeanwd.ndarray( 4, x, 2, 1 );
 // returns 1.25
 ```