.oniro-ci: switch to oniro manifest mirror

During workspace construction, the .workspace job relies on a git-repo
mirror which tracks all of the repositories described by the manifest.
Those mirrors are maintained externally in the infrastructure of the
continuous integration system. Switch to the mirror which tracks the
manifests from booting.onrioproject.org.

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