refactor: use an object spread instead of Object.assign (#6939)

Co-authored-by: Jay <jasonsaayman@gmail.com>

bin/RepoBot.js

@@ -24,9 +24,10 @@ class RepoBot {
       templates
     } = options || {};
 
-    this.templates = Object.assign({
-      published: NOTIFY_PR_TEMPLATE
-    }, templates);
+    this.templates = {
+      published: NOTIFY_PR_TEMPLATE,
+      ...templates
+    };
 
     this.github = api || new GithubAPI(owner, repo);