Make context drawer non-interactive

It's interactive by default, which generates a column of dead pixels on
the right side, per https://bugs.kde.org/show_bug.cgi?id=468211.

Since the issue hasn't been fixed upstream yet, let's disable
interactivity in Elisa to work around it. We won't lose anything since
nobody swipes from the side to show the drawer in Elisa, which has a
dedicated mobile UI for small touch devices.

CCBUG: 468211