Remove obsolete video_url column in poll_questions table

This column isn't used since commit 4c0deb0ec because administrators can
associate videos to the answers since commit 5862eea51. The value of
this attribute isn't used in the public area since commit 8277e3cc2.

db/migrate/20250222222739_remove_poll_questions_video_url.rb

@@ -0,0 +1,5 @@
+class RemovePollQuestionsVideoUrl < ActiveRecord::Migration[7.0]
+  def change
+    remove_column :poll_questions, :video_url, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2024_10_26_112901) do
+ActiveRecord::Schema[7.0].define(version: 2025_02_22_222739) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
   enable_extension "plpgsql"
@@ -1138,7 +1138,6 @@ ActiveRecord::Schema[7.0].define(version: 2024_10_26_112901) do
     t.datetime "created_at", precision: nil
     t.datetime "updated_at", precision: nil
     t.tsvector "tsv"
-    t.string "video_url"
     t.index ["author_id"], name: "index_poll_questions_on_author_id"
     t.index ["poll_id"], name: "index_poll_questions_on_poll_id"
     t.index ["proposal_id"], name: "index_poll_questions_on_proposal_id"