Remove TODO from databases

Author: samdark

src/guide/index.md

@@ -14,7 +14,7 @@ We release this guide under the [Terms of Yii Documentation](https://www.yiifram
 - [Running applications](start/workflow.md)
 - [Saying hello](start/hello.md)
 - [Working with forms](start/forms.md)
-- [Working with databases](start/databases.md) TODO
+- [Working with databases](start/databases.md)
 - [Generating code with Gii](start/gii.md) TODO
 - [Looking ahead](start/looking-ahead.md)