Fix meta class on models extending `PluginDataModel`

This model will not have an index on `plugin_data` field:

```python
class SomeModel(PluginDataModel)
    ...

    class Meta:
        ordering = ["-id"]
```

Fix:

```python
class SomeModel(PluginDataModel)
    ...

    class Meta(PluginDataModel.Meta):
        ordering = ["-id"]
```

Fix should also include updated migrations for new models