[FIX] web_editor: prevent o-apply-colors to force important rules

The mixin was inconsistent: depending on the color, the created rules
were `!important` or not. This causes bugs with new master features.

closes odoo/odoo#54151

X-original-commit: 83d8c8b66bd9e58b08fe0aa66d2be7bab691ce3e
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/scss/web_editor.variables.scss

@@ -437,6 +437,6 @@ $o-color-extras-nesting-selector: '&, .o_colored_level &';
         // be avoided and use the class in XML if possible.
         @extend .o_cc#{$-related-color};
     } @else {
-        @include o-bg-color(o-color($-related-color), $background: $background);
+        @include o-bg-color(o-color($-related-color), $background: $background, $important: false);
     }
 }