This commit removes the field twitter_hashtag from event and event_type. The justification behind this change is that it has been made obsolete by our social marketing app and our website builder. Task ID 2191921 Community PR odoo/odoo#44715 Upgrade PR odoo/upgrade#764 Related: odoo/upgrade#764 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>