docs: remove definition

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

Author: kgryte

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

@@ -138,8 +138,6 @@ console.log( v );
 
 [arithmetic-mean]: https://en.wikipedia.org/wiki/Arithmetic_mean
 
-[@higham:1993a]: https://doi.org/10.1137/0914050
-
 </section>
 
 <!-- /.links -->