Makefile: add v prefix to version read from VERSION file
Makefile: add v prefix to version read from VERSION file

Previous I added the prefix directly in `docker-image` target.
But that doesn't make sense if you override the `RELEASE_TAG`.

Signed-off-by: Jakub Sokołowski <1d3764b91b902f6b45836e2498da81fe35caf6d6@status.im>

status-im/status-go,status-im/status-go,status-im/status-go