gitmodules: Correct libvirt-ci submodule URL

gitmodules: Correct libvirt-ci submodule URL

Correct the libvirt-ci repository URL to avoid this warning when
cloning / refreshing the submodule:

  warning: redirecting to https://gitlab.com/libvirt/libvirt-ci.git/

Fixes: 4ebb040f1fd ("tests: integrate lcitool for generating build env manifests")
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220121154134.315047-3-f4bug@amsat.org>
Message-Id: <20220204204335.1689602-7-alex.bennee@linaro.org>