travis.yml: Refresh the x86 32-bit test list

With the new QEMU from Ubuntu Focal, we can now run additional
tests that were failing before.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201001072234.143703-3-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>