[IMP] web_editor: consider common colors as custom when used in the page

Before this commit, if the user chose the "red" color suggestion, "red"
did not appear as a custom color (but the color suggestion was marked
as selected). This made sense in the previous colorpalette widgets but
not anymore as the suggestions do not always appear in all colorpickers
anymore.

Now those colors are always considered custom when used in the page and
at worst appear as "common" and "custom" at the same time (the "common"
one being the one which can appear as selected in that case).

Part of https://github.com/odoo/odoo/pull/67545
task-2476601

closes odoo/odoo#67545

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

addons/web_editor/static/src/js/wysiwyg/widgets/color_palette.js

@@ -38,7 +38,6 @@ const ColorPaletteWidget = Widget.extend({
      */
     init: function (parent, options) {
         this._super.apply(this, arguments);
-        this.customColorsArray = [].concat(...customColors);
         this.style = window.getComputedStyle(document.documentElement);
         this.options = _.extend({
             selectedColor: false,
@@ -254,9 +253,7 @@ const ColorPaletteWidget = Widget.extend({
             return;
         }
         this.el.querySelectorAll('.o_custom_color').forEach(el => el.remove());
-        const existingColors = new Set(this.customColorsArray.concat(
-            Object.keys(this.colorToColorNames)
-        ));
+        const existingColors = new Set(Object.keys(this.colorToColorNames));
         this.trigger_up('get_custom_colors', {
             onSuccess: (colors) => {
                 colors.forEach(color => {