[FIX] web: Wrong comparison in invoice analyes

Steps to reproduce the bug:
Let's consider that we are in 2019

- Create two customer invoices: I1 and I2
- I1 with invoice date = 2 april 2019 and amount = 100€
- I2 with invoice date = 2 april 2018 and amount = 1000€
- Go to Reporting > Invoices
- Click on widget "Time Ranges" and set "Based on" Invoice Date and "Range" This Year "Compare To" Previous Year

Bug:

The untaxed total for previous year was 1100€ instead of 1000€ because it counted previous year and this year.

opw:1962027

closes odoo/odoo#32331

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

addons/web/static/src/js/core/domain.js

@@ -258,8 +258,8 @@ var Domain = collections.Tree.extend({
                     });
                     break;
                 case 'previous_year':
-                    leftBoundaryParams.years = leftBoundaryParams.years ? leftBoundaryParams.years-- : -1;
-                    rightBoundaryParams.years = rightBoundaryParams.years ? rightBoundaryParams.years-- : -1;
+                    leftBoundaryParams.years = leftBoundaryParams.years ? leftBoundaryParams.years - 1 : -1;
+                    rightBoundaryParams.years = rightBoundaryParams.years ? rightBoundaryParams.years - 1 : -1;
                   break;
             }