update README.md

Author: abhishekblue

lib/node_modules/@stdlib/stats/incr/nangmean/README.md

@@ -48,7 +48,7 @@ The [geometric mean][geometric-mean] is defined as the nth root of a product of
 ## Usage
 
 ```javascript
-var incrnangmean = require( '@stdlib/stats/incr/gmean' );
+var incrnangmean = require( '@stdlib/stats/incr/nangmean' );
 ```
 
 #### incrnangmean()