Increase max file size of url downloader proxy to 1010mb

If you look at git show
b06baad758aca^:modules/url-downloader/files/copy-by-url-proxy.conf
you will notice a code comment saying make it slightly larger
than the max upload size. Since that time the max upload size has
increased to 1000mb, so increase this limit in turn.

Of course people trying to upload 1 gb big files may still run
into various timeouts.

Bug: 73200
Change-Id: Ib83d9dbfe87ea4e3d673b712aa3d8d3727c9ce36