[FIX] account: Fix manual tax entry display bug

Problem
---------
Fix a display bug happening when manually modifying taxes in bills.

Objective
---------
Get the same behavior as in 15.2

Solution
---------
Colspan was acting weird when clicking the tax to input. It would
expand to the full size allowed. To avoid this behavior, I made the tax
display width to 0%. This makes it impossible for the input to expand
upon clicking.

task-3397951

closes odoo/odoo#128774

Signed-off-by: Laurent Smet (las) <las@odoo.com>