Auto-disable "border" setting when rendering with VSE

Just a minor nitpick that should be very easy to fix.

When I render something in the VSE, having "border" enabled makes Blender unceremoniously spit out the following error:

"Border rendering is not supported by sequencer"

This can happen if the user has "border" enabled in Cycles, then switches to the VSE to do something else. In addition, I like to keep the "border" mode enabled by default for convenience since it improves Cycles' viewport responsiveness when looking through a camera. Naturally, I run into this error a lot and it has me wondering why it's there.

I don't see why it can't just ignore the border setting since it has nothing to do with the sequencer; it doesn't even exist in the VSE.* If ambiguity of the behavior is really an issue here, I think it would be fine to quietly show a message that says "border setting is ignored in sequence renders" and proceed with the render instead of stopping the user in their tracks and forcing them to go and click a checkbox.

*Actually, apparently it does (hit space -> type border). Either way, it doesn't seem to do anything anyway, in which case it might as well be removed completely.