[FIX] web_editor: specify a custom color in the text input of the color picker.

Before this commit:

It's impossible to specify a custom color in the text input of the color picker
for the selected text.

After this commit:

It's possible to specify a custom color in the text input of the color picker
for the selected text.

Task-2896109

closes odoo/odoo#98548

Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>