tests/vm: remove ubuntu.i386 VM test

tests/vm: remove ubuntu.i386 VM test

Ubuntu 18.04 is out of our support window, and Ubuntu 20.04 does not
support i386 anymore. The debian project does, but they do not provide
any cloud images for it, a new expect-style script would have to be
written.

Since we have i386 cross-compiler tests hosted on GitLab CI, we don't
need to support this VM test anymore.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220708153503.18864-7-jsnow@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>