[FIX] web: preview PDF file on iOS

Before this commit, the end users were unable to click on the
kanban image to see document's preview.

To fix this we removed lines from a previous fix which is no
longer useful in 13.0 because we now use kanban views for
many2X fields instead of list views.
See original commit:
https://github.com/odoo/odoo/commit/26c62cbb4401bffb72ce77fee481ca84b77a8143
So for mobile phones it's working fine.

For iPads, this rule is no longuer necessary since iPadOS.
See "Accelerated Scrolling on iOS and iPadOS":
https://webkit.org/blog/9674/new-webkit-features-in-safari-13/
For previous versions it still works because the DOM has changed.

Steps to reproduce:
- Go to Document
- Click on "o_kanban_image"
=> Your're stuck on a grayed page.

opw-2260101

closes odoo/odoo#56977

X-original-commit: 0d41d0daa7220a791bc4df85cca4100e3634e432
Related: odoo/enterprise#12907
Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/web/static/src/scss/modal.scss

@@ -122,8 +122,6 @@
 }
 
 body.modal-open {
-    // Allow vertical scrolling in modals on iOS
-    -webkit-overflow-scrolling: touch;
     .modal {
         @include o-scrollbar-overlay;
     }