REFACTOR: Remove an unused Topic model observer (#9723)

REFACTOR: Remove an unused Topic model observer (#9723)

As far I can tell nothing sets categoryName on the Topic model. Didn’t find anything in all-the-plugins/all-the-themes either.

diff --git a/app/assets/javascripts/discourse/app/models/topic.js b/app/assets/javascripts/discourse/app/models/topic.js
index 573104b..f7ec6ea 100644
--- a/app/assets/javascripts/discourse/app/models/topic.js
+++ b/app/assets/javascripts/discourse/app/models/topic.js
@@ -236,16 +236,6 @@ const Topic = RestModel.extend({
     this.set("category", Category.findById(this.category_id));
   },
 
-  @observes("categoryName")
-  _categoryNameChanged() {
-    const categoryName = this.categoryName;
-    let category;
-    if (categoryName) {
-      category = this.site.get("categories").findBy("name", categoryName);
-    }
-    this.set("category", category);
-  },
-
   categoryClass: fmt("category.fullSlug", "category-%@"),
 
   @discourseComputed("tags")

GitHub sha: a2bb33b6

This commit appears in #9723 which was approved by eviltrout. It was merged by CvX.