.gitlab-ci.yml: Use the inherited git configuration from the container image

The container image already defines the user and the email for the builder's/CI's git operations[1] so there is no need to override it here and have to maintain two places for this identity.

[1]https://gitlab.eclipse.org/eclipse/oniro-core/oniro/-/blob/kirkstone/.oniro-ci/containers/bitbake-builder/Dockerfile

Fixes oniro#513 (closed)

Signed-off-by: Andrei Gherzan andrei.gherzan@huawei.com