[IMP] demo: move the pivot sheet up

In the demo data, the sheet with a pivot is the 7th sheet. It means
that on small screen/with dev tools open, the sheet is not visible
in the bottom bar without scrolling. It's quite annoying, as this
sheet is very useful when developing/debugging pivot feature.

And arguably, the pivot feature is one of the most important feature of
o-spreadsheet, and should be highlighted in the demo.

This commit moves up the pivot sheet so it's one of the first you see.

closes #8087

Task: 6022909
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>

Author: hokolomopo