Apply suggestion from @kou

Remove assignment to unused variable

Co-authored-by: Sutou Kouhei <kou@cozmixng.org>

Author: tompng

lib/rdoc/generator/template/aliki/js/aliki.js

@@ -242,7 +242,6 @@ function hookTocActiveHighlighting() {
 
     // Add active class to current link
     correspondingLink.classList.add('active');
-    activeLink = correspondingLink;
 
     // Scroll link into view if needed
     var tocNav = document.querySelector('#toc-nav');