With the recent refactorings to `GitClient`, where singletons
are created and can be retrieved through a static method, the
test has been updated to also install spies for the static methods
of `GitClient`. This commit updates the spy installation so that
the same mock git client is used that is also passed manually to
the release actions. Having two separate instances of the mock
git client could result in false-positive test results.
PR Close#42468