[IMP] web_editor: shape - merge some style + fix color

Blocks and Rainy / Airy and Zigs merged together
Fix color of Bold 5 and bold 6 shape that are not easy to use due to contrast
with black, now it is grey by default.

task-2357174

closes odoo/odoo#62338

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>