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

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: 2023_02_17_084310) do
+ActiveRecord::Schema[7.0].define(version: 2023_02_23_115536) do
   create_table "donations", force: :cascade do |t|
     t.integer "user_id"
     t.integer "amount_sats"