docs: update example

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

Author: kgryte

lib/node_modules/@stdlib/_tools/eslint/rules/tsdoc-declarations-doctest/README.md

@@ -74,8 +74,6 @@ declare function add( x: number, y: number ): number;
 * // returns 5
 */
 declare function add( x: number, y: number ): number;
-
-export = add;
 ```
 
 </section>