Right - this is more of a sticking point for 8.0 than it's previously been, but doing an upgrade or restoring a .gwbk keeps your old JDBC drivers. The reasoning behind this is, it would be worse to install the new version (or restore a backup from a running system) and suddenly your databases no longer work.
You will have to manually update the JDBC driver in order to obtain the new version, and then your .gwbks from that point on will have that new version.