Update start-workflow.md (yiisoft#16573) [skip ci]

It's not only possible, but quite normal, that an action loads more than one data model. Using the singular, suggesting that it (necessarily or typically) loads only one model, is confusing.

You may want to consider these alternatives:
- "The action loads zero or more data models"
- "The action optionally loads one or more data models"

but I guess "some models" is clear enough.

docs/guide/start-workflow.md

@@ -95,8 +95,8 @@ The following diagram shows how an application handles a request.
 5. The controller creates an [action](structure-controllers.md) instance and performs the filters for the action.
 6. If any filter fails, the action is cancelled.
 7. If all filters pass, the action is executed.
-8. The action loads a data model, possibly from a database.
-9. The action renders a view, providing it with the data model.
+8. The action loads some data models, possibly from a database.
+9. The action renders a view, providing it with the data models.
 10. The rendered result is returned to the [response](runtime-responses.md) application component.
 11. The response component sends the rendered result to the user's browser.