DEV: Drop user_id from chat_mentions (#25022)

This column is ignored since 62f423d

plugins/chat/db/post_migrate/20240410130000_drop_user_id_from_chat_mentions.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class DropUserIdFromChatMentions < ActiveRecord::Migration[7.0]
+  DROPPED_COLUMNS ||= { chat_mentions: %i[user_id] }
+
+  def up
+    DROPPED_COLUMNS.each { |table, columns| Migration::ColumnDropper.execute_drop(table, columns) }
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end