Merge pull request #7842 from obregonia1/fix-n-plus-one

N+1 が発行されていたので対応

app/controllers/courses/practices_controller.rb

@@ -3,7 +3,7 @@
 class Courses::PracticesController < ApplicationController
   def index
     @course = Course.find(params[:course_id])
-    @categories = @course.categories.order(:created_at)
+    @categories = @course.categories.includes(practices: %i[practices_books learning_minute_statistic started_students]).order(:created_at)
     @learnings = current_user.learnings
   end
 end