Remove subscription_expires_at leftover from OStatus (#15857)

db/post_migrate/20210308133107_remove_subscription_expires_at_from_accounts.rb

@@ -0,0 +1,7 @@
+class RemoveSubscriptionExpiresAtFromAccounts < ActiveRecord::Migration[5.0]
+  def change
+    safety_assured do
+      remove_column :accounts, :subscription_expires_at, :datetime, null: true, default: nil
+    end
+  end
+end