aws-iam-authenticator: Fix checkver

[niheaven]

#150

[tynril]

TL;DR: The releases are also on GitHub: https://github.com/kubernetes-sigs/aws-iam-authenticator/releases -- this might allow simplifying the version check.

The current version on Scoop (2019-08-22) seems to map to 0.4.0: running aws-iam-authenticator version returns {"Version":"v0.4.0","Commit":"c141eda34ad1b6b4d71056810951801348f8c367"}, which is the correct commit for release v0.4.0 on the aforementioned GitHub.

That being said, the executable that Scoop currently downloads is not the same as the one the GitHub release provides:

λ ls | Get-FileHash -Algorithm SHA256 | Format-Table

Algorithm       Hash                                                                   Path
---------       ----                                                                   ----
SHA256          9014193536BC97B79BF8D5540954548704453648BBA63D74AC63E0B0F32AAB49       aws-iam-authenticator.exe
SHA256          D26CCD0E83667F79DEA88A72072371FD87C2023895417B54C2BD0E4C55D7D5FA       aws-iam-authenticator_0.4.0_windows_amd64.exe

And while they are both 0.4.0, they use two different commits (with 9999cd being the one right before c141eda):

λ .\aws-iam-authenticator.exe version
{"Version":"v0.4.0","Commit":"c141eda34ad1b6b4d71056810951801348f8c367"}
~\Desktop
λ .\aws-iam-authenticator_0.4.0_windows_amd64.exe version
{"Version":"0.4.0","Commit":"9999cd8047782c94c08e2d24b77dc9488947aa03"}

Presumably, Amazon uploaded a different build made on the previous commit to the repository for their documentation. I've used the GitHub version for a bit and everything behaves as expected (which is to say, the same way as the version currently on Scoop).

[tynril]

I just made a separate PR for the same issue using GitHub instead of a regex: #668

[rasa]

Close this and go with #668 instead?