[FIX] web_editor: fix FIELD_IS_DIRTY notification on historystep

Fixes an issue introduced in a forward-port:
https://github.com/odoo/odoo/commit/db0c092973f480f3336a44e5f6868dc5a79f0e3a
The listener was not set on the correct target, `historyStep` event is triggered
on `odooEditor` and not `odooEditor.editable`.

This meant that the FormStatusIndicator was not properly notified and
the `save/discard` button was not visible after an editor `historyStep` on form
views

task-3373603

closes odoo/odoo#126006

X-original-commit: f76585530d7387ff2f44639252829aa4546cea1b
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/web_editor/static/src/js/backend/html_field.js

@@ -337,7 +337,7 @@ export class HtmlField extends Component {
             this.wysiwyg.toolbar.$el.append($codeviewButtonToolbar);
             $codeviewButtonToolbar.click(this.toggleCodeView.bind(this));
         }
-        this.wysiwyg.odooEditor.editable.addEventListener("historyStep", () =>
+        this.wysiwyg.odooEditor.addEventListener("historyStep", () =>
             this.props.record.model.bus.trigger("FIELD_IS_DIRTY", this._isDirty())
         );