Mini fixes

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.2+
| Fixed tickets | -

*form_customization*
Preceding code lines are not related to what the code demonstrates: Twig blocks do not need to be defined in separate files; the file does not hold a form, so importing a theme is confusing

*monolog*
Standard Edition uses lowercase `error` value in `config_prod.yml`