Fosshost is mostly dead and can be removed from the page, but lately QEMU
has received important sponsorships from GNOME and Azure, so mention them.
OSUOSL also provides OpenStack virtual machines to QEMU.

Our CI resources are sponsored by WorksOnArm, the IBM LinuxOne community
cloud and GitLab.

Finally, include directions for people that want to sponsor QEMU or
donate money to the project.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>