[FIX] spreadsheet_dashboard_account: display unpaid amount absolute value

In the Invoicing dashboard, the upper-left most scorecard displays the total
invoiced amount.
The baseline "X unpaid" is wrong. It was displaying the difference between
the key value (total invoiced amount) and the unpaid amount.
That means if not a single invoice was paid (everything unpaid), it would
display "0 unpaid". That obviously not correct.

opw-3248761

closes odoo/odoo#118030

X-original-commit: 2b795ee59ef063b5b7298382008ebd61c51de36e
Signed-off-by: Lucas Lefèvre (lul) <lul@odoo.com>

addons/spreadsheet_dashboard_account/data/files/invoicing_dashboard.json

@@ -1281,7 +1281,7 @@
                     "data": {
                         "baselineColorDown": "#DC6965",
                         "baselineColorUp": "#00A04A",
-                        "baselineMode": "difference",
+                        "baselineMode": "text",
                         "title": "Invoiced",
                         "type": "scorecard",
                         "baseline": "Data!C11",