Fix rollback for few migrations

Few IrreversibleMigrationException exceptions throws:

- Column type "mediumtext" is not supported by MySQL
- Cannot reverse a "Phinx\Db\Action\ChangeColumn" command
- Cannot reverse a "Phinx\Db\Action\RemoveColumn" command
- Cannot reverse a "Phinx\Db\Action\DropIndex" command

Few MySQL errors:

- Cannot drop index '...': needed in a foreign key constraint
- Can't DROP 'type'; check that column/key exists

Older migrations were fixed just to prevent copy -> paste errors in
future.

src/migrations/20220530121649_nullable_family_subscription_types_slave_subscription_type_id.php

@@ -4,10 +4,17 @@
 
 class NullableFamilySubscriptionTypesSlaveSubscriptionTypeId extends AbstractMigration
 {
-    public function change()
+    public function up()
     {
         $this->table('family_subscription_types')
             ->changeColumn('slave_subscription_type_id', 'integer', ['null' => true])
             ->update();
     }
+
+    public function down()
+    {
+        $this->table('family_subscription_types')
+            ->changeColumn('slave_subscription_type_id', 'integer', ['null' => false])
+            ->update();
+    }
 }