Upgrade git-crypt to 0.6.0
Upgrade git-crypt to 0.6.0

Hi Concourse team!
We're using `git-crypt` in our pipeline and we are being hit by [this bug](https://github.com/AGWA/git-crypt/issues/71) which was fixed by [this commit](https://github.com/AGWA/git-crypt/commit/b47176e6a8b202380cb11fa3d0b2fd7331ead029). Also, `0.5.0` is very old (2015!) so it's probably worth to upgrade! Thanks :)
concourse/git-resource