Remove ln_login from users

Not needed anymore, removing in favor of unencrypted `ln_account`.

db/migrate/20230223115536_remove_ln_login_from_users.rb

@@ -0,0 +1,5 @@
+class RemoveLnLoginFromUsers < ActiveRecord::Migration[7.0]
+  def change
+    remove_column :users, :ln_login_cyphertext
+  end
+end