Updating crypto lib

[emanation]

https://github.com/jtblin/kube2iam/blob/master/go.mod#L28

Outdated module golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 causing security alert.
https://nvd.nist.gov/vuln/detail/CVE-2020-9283
Can this be updated?