Update download link please

[David Ecker <david@diskwait.com>]

Hello,

The '64-bit PC netinst iso' link on the page
https://www.debian.org/distrib I think needs to point to 7.5.0 from 7.4.0.

Thanks,
David

P.S. It looks like the 32-bit PC netinst iso should be fixed as well.