Don't log the git commands in the version updater Go code. They are already
shown by the Makefile (`update-version` target), and we should only have
one set of those commands to maintain.
Flamenco now no longer uses the Git tags + hash for the application
version, but an explicit `VERSION` variable in the `Makefile`.
After changing the `VERSION` variable in the `Makefile`, run
`make update-version`.
Not every part of Flamenco looks at this variable, though. Most
importantly: the Blender add-on needs special handling, because that
doesn't just take a version string but a tuple of integers. Running
`make update-version` updates the add-on's `bl_info` dict with the new
version. If the version has any `-blabla` suffix (like `3.0-beta0`) it
will also set the `warning` field to explain that it's not a stable
release.
