landing_page: Switch to sidebar menu earlier at width <= 1024px.
landing_page: Switch to sidebar menu earlier at width <= 1024px.

Right now, some of our horizontally spaced out top-level dropdowns
(such as "Solutions") get truncated on screen widths less than
1024 px. We switch to the vertical sidebar menu at widths less than
686px.

Looking at a lot of mainstream websites, a few of them switch to a
vertical sidebar menu on much wider widths than we do. Plus,
switching to a vertical orientation is a much cleaner way to fix
this issue than playing around with legacy Bootstrap code. Therefore,
we should toggle on the sidebar menu at width <= 1024px.

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