[FIX] web_editor: keep "Outline + Rounded" style when editing link

Before this commit editing a link that was saved with the style "Outline
+ Rounded" did reset the style to as different value.

After this commit "Outline + Rounded" is not lost when re-editing the
link.

task-2629461

closes odoo/odoo#75398

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>