Before this commit, every view had to have its own rules to avoid
breaking the control panel when there was an horizontal scroll.
a) We now always use 'overflow-x: auto' to be able to scroll the content
of the view if there is not enough space available.
However, we doesn't want double vertical scroll; one for the page and
another one for the content. It's why we added visible to the previous rule:
"overflow-x: auto visible".
b) overflow: visible; is the default value. We simply deleted this line.
c) We need to set height: 100%; to allow the pivot view to grow when a
dropdown pops out. Otherwise, it will be cutted.
Steps to reproduce:
* Go to Sale
* Select the 'Pivot' view
* Add 'Customer' to group horizontally
* Scroll to the right => BUG
Task ID: 2232265
closesodoo/odoo#75826
Related: odoo/enterprise#18121
Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>