Minor upgrade done to match the version deployed in CI due to a bug
with `nix-copy-closure` which broken Nix cache jobs:
https://github.com/status-im/infra-ci/issues/49
This will not force upgrade on developes, nor require any `make nix-purge`.
If however and upgrade is wanted it can be simply done with `nix upgrade-nix`.
Signed-off-by: Jakub Sokołowski <jakub@status.im>