[FIX] web_editor: apply changes on exit code view

When leaving the code view, we need to apply its html to the editable.
This failed in mass_mailing because the editor rolled back the changes
due to the top element being unremovable. To avoid that, we set the
`skipRollback` argument of `historyStep` to `true` and thereby trust the
user's changes.

task-2701024

closes odoo/odoo#80522

X-original-commit: 17f0ca0d6b7a583192caa33bb9d3e35c72256d4e
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>
Signed-off-by: Antoine Guenet <age@odoo.com>

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

@@ -228,7 +228,7 @@ var FieldHtml = basic_fields.DebouncedField.extend(TranslatableFieldMixin, {
             }
             this.wysiwyg.odooEditor.observerActive();
             this.wysiwyg.setValue($codeview.val());
-            this.wysiwyg.odooEditor.historyStep();
+            this.wysiwyg.odooEditor.historyStep(true);
         } else {
             this.resizerHandleObserver = new MutationObserver((mutations, observer) => {
                 for (let mutation of mutations) {