[FIX] web_editor: fix button size restored when focused

Steps to reproduce the bug :
    - In Website (edit mode), drag & drop a "text-image" snippet.
    - Click on the button.
    - Change the size of the button to "small".
    - Click outside the button.
    - Re-click on the button.
    - The size selected in the options is "medium" and not "small".

Note that the same bug exist in backend with the link dialog.

This bug was introduced in ([1]), the code of the "else" (which was
removed by it) made it possible to take into account the cases where the
option had no "value" (e.g. "medium" size button). And so, without this
"else", the options without "value" were activated in any case.

This previous commit, which fixed an issue with the presence of the
"btn-success" class on a link, could in fact be based on what had
already been done for the links with the "btn-link" class (in [2]).

In this commit, this issue with the "btn-success" class is handled the
same way as for "btn-link".

[1]: https://github.com/odoo/odoo/commit/4c68b3e923610e1d573b4bd2b241b2fc5923c412
[2]: https://github.com/odoo/odoo/commit/c3e08e7a7baab1035c3d5c48d668cc02a232e1ac



task-3002177

closes odoo/odoo#102632

Signed-off-by: Outagant Mehdi (mou) <mou@odoo.com>