Call renderLinkedName directly from renderCategoryLabel

This avoids calling back to Category, which immediately calls the
renderer again anyway, except that during a test the second call went
to an html renderer because the packageGraph was holding a
HtmlRendererFactory.

Author: jdkoren

lib/src/render/category_renderer.dart

@@ -31,7 +31,7 @@ class CategoryRendererHtml extends CategoryRenderer {
 
     StringBuffer buf = StringBuffer();
     buf.write('<span class="${spanClasses.join(' ')}" title="$spanTitle">');
-    buf.write(category.linkedName);
+    buf.write(renderLinkedName(category));
     buf.write('</span>');
     return buf.toString();
   }
@@ -49,7 +49,7 @@ class CategoryRendererHtml extends CategoryRenderer {
 
 class CategoryRendererMd extends CategoryRenderer {
   @override
-  String renderCategoryLabel(Category category) => category.linkedName;
+  String renderCategoryLabel(Category category) => renderLinkedName(category);
 
   @override
   String renderLinkedName(Category category) {