[IMP] developer/*: update js code to ES6

This PR updates javascript code to be up to date with the codebase standards:
- use the `static` keyword when possible
- proper owl imports
- removed unecessary `@odoo-module` directives

Task ID: 2258359

closes odoo/documentation#11466

Signed-off-by: Bastien Fafchamps (bafa) <bafa@odoo.com>

content/developer/howtos/website_themes/building_blocks.rst

@@ -380,8 +380,6 @@ The `data-js` attribute can be assigned to an options group in order to define a
 
 .. code-block:: javascript
 
-   /** @odoo-module */
-
    import options from 'web_editor.snippets.options';
 
    options.registry.CustomMethodName = options.Class.extend({