text: Title: auto migrations fails when table in schema
  Body: Hello,
  I'm running the latest Postgres image, python 3.11.3 (venv) and piccolo 0.119.0.
  When i create a new asgi application with a fresh venv, i can perfectly add, change and delete rows using the migrations new .. --auto / forward command. Then i can migrate the table into a schema e.g. `class Task(Table, schema="blog"):`, running forward will succefully put the table into that schema. But as soon as it is in a schema i'm not able to perform any auto migrations anymore. It won't find that table:
  ```
    - 2023-09-08T14:20:15:789180 [forwards]... The command failed.
  relation "task" does not exist
  Traceback (most recent call last):
    File "C:\venvs\piccolodb\Lib\site-packages\targ\__init__.py", line 448, in run
      command.call_with(arg_class)
    File "C:\venvs\piccolodb\Lib\site-packages\targ\__init__.py", line 229, in call_with
      asyncio.run(self.command(**cleaned_kwargs))
    File "C:\Program Files\Python311\Lib\asyncio\runners.py", line 190, in run
      return runner.run(main)
             ^^^^^^^^^^^^^^^^
    File "C:\Program Files\Python311\Lib\asyncio\runners.py", line 118, in run
      return self._loop.run_until_complete(task)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\Program Files\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete
      return future.result()
             ^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\commands\forwards.py", line 159, in forwards
      response = await run_forwards(
                 ^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\commands\forwards.py", line 120, in run_forwards
      response = await manager.run()
                 ^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\commands\forwards.py", line 97, in run
      return await self.run_migrations(app_config)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\commands\forwards.py", line 82, in run_migrations
      await response.run()
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\auto\migration_manager.py", line 863, in run
      await self._run_drop_columns(backwards=backwards)
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\auto\migration_manager.py", line 642, in _run_drop_columns
      await self._run_query(
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\apps\migrations\auto\migration_manager.py", line 393, in _run_query
      await query.run()
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\query\base.py", line 445, in run
      return await engine.run_ddl(self.ddl[0], in_pool=in_pool)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\piccolo\engine\postgres.py", line 553, in run_ddl
      response = await current_transaction.connection.fetch(ddl)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\asyncpg\connection.py", line 620, in fetch
      return await self._execute(
             ^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\asyncpg\connection.py", line 1659, in _execute
      result, _ = await self.__execute(
                  ^^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\asyncpg\connection.py", line 1684, in __execute
      return await self._do_execute(
             ^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\venvs\piccolodb\Lib\site-packages\asyncpg\connection.py", line 1731, in _do_execute
      result = await executor(stmt, None)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "asyncpg\protocol\protocol.pyx", line 201, in bind_execute
  asyncpg.exceptions.UndefinedTableError: relation "task" does not exist
  ```
  
  I can change the migration_file from
  ````
  from piccolo.apps.migrations.auto.migration_manager import MigrationManager
  
  
  ID = "2023-09-08T14:20:15:789180"
  VERSION = "0.119.0"
  DESCRIPTION = ""
  
  
  async def forwards():
      manager = MigrationManager(
          migration_id=ID, app_name="home", description=DESCRIPTION
      )
  
      manager.drop_column(
          table_class_name="Task",
          tablename="task",
          column_name="completed_at",
          db_column_name="completed_at",
      )
  
      return manager
  
  ````
  
  to 
  
  ````
  ....
      manager.drop_column(
          table_class_name="Task",
          tablename="blog.task",
          column_name="completed_at",
          db_column_name="completed_at",
      )
  
      return manager
  
  ````
  it will perform the migration. Any clues what's going on here?