Hi,

After a quick look not able to see a place/menu where you can delete this records. (not sure whether there is option is available or not)

As a work around what you can do is that, activate the developer mode and navigate to Settings -> Technical -> User Interface -> Menu Items, here you an create a new menu by clicking the create button. 

Give the menu name as Tags or Account Tags, then in the parent you can choose the parent where you need this menu, better choose Invoicing/Configuration as Parent. In the actions choose ir.actions.act_window and in next field choose the record Account Tags as the action, save it.

Now if you go to Invoicing -> Configuration -> open the menu you have created, here you can see all the tags and rename or delete it accordingly.

UPDT: OR you can download and use this module from OCA: https://www.odoo.com/apps/modules/12.0/account_tag_menu/

Thanks