added missing index in FeedPosts

db/migrate/20241022002658_add_feed_posts_post_index.rb

···
+class AddFeedPostsPostIndex < ActiveRecord::Migration[6.1]
+  def change
+    add_index :feed_posts, :post_id
+  end
+end

db/schema.rb

···
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2024_10_17_135717) do
+ActiveRecord::Schema[8.0].define(version: 2024_10_22_002658) do
   create_table "feed_posts", force: :cascade do |t|
     t.integer "feed_id", null: false
     t.integer "post_id", null: false
     t.datetime "time", precision: nil, null: false
     t.index ["feed_id", "time"], name: "index_feed_posts_on_feed_id_and_time"
+    t.index ["post_id"], name: "index_feed_posts_on_post_id"
   end
 
   create_table "posts", force: :cascade do |t|