Fix mobile navigation issue

This MR removes the resize event handler for the sidebar navigation.

Why

We had a window resize handler which automatically closed the side navigation if a user resizes the browser window to a smaller size.

This caused an issue on mobile devices where the side navigation would automatically close when the page is scrolled upwards. The reason being is that it seems like a resize event gets fired by the mobile browser when the address bar is displayed upon scrolling upwards.

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