SystemOTA tries to stay compatible with Yocto Dunfell which currently
provides Go 1.14. The test pipeline was following latest version of Go.
We should test against 1.14 and later versions equally.

Fixes: https://booting.oniroproject.org/distro/components/sysota/-/issues/57


Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>