Note that in 14.0 the same fix was already applied with [1]. This commit
only clarifies the line's related comment and use the right zindex
variable (even though the value is the same).

[1]: https://github.com/odoo/odoo/commit/0f2cab4aebcc33ca9e278c9395fed2cc8934ed38



closes odoo/odoo#61866

X-original-commit: 702f2b93
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>
Co-authored-by: qsm-odoo <qsm@odoo.com>