Update google-cloud-env from 1.5.0 to 1.6.0

What does this MR do and why?

Updates google-cloud-env from 1.5.0 to 1.6.0, which allows us to use Faraday v2 in the future.

google-cloud-env is used from fog-google gem.

Diff in the upstream: https://github.com/googleapis/ruby-cloud-env/compare/google-cloud-env/v1.5.0...google-cloud-env/v1.6.0

Part of #369862 (closed)

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