[FIX] web_editor: do not allow we-checkbox to shrink below checkbox size

E.g. the scrolltop button option has a checkbox followed by a select
on the same row and the checkbox was partly cut because of it.

Part of https://github.com/odoo/odoo/pull/60271
task-2312878

X-original-commit: 70570c69989b49b8ab89d71ea89d19195e3028ae

addons/web_editor/static/src/scss/wysiwyg_snippets.scss

@@ -742,6 +742,7 @@ body.editor_enable.editor_has_snippets {
 
         // Checkboxes
         we-button.o_we_checkbox_wrapper.o_we_user_value_widget {
+            min-width: $o-we-sidebar-content-field-toggle-width;
             padding: 0;
             border: none;
             background: none;