Update dependency go to v1.21.6

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
go (source)	golang	patch	1.21.5 -> 1.21.6

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Release Notes

golang/go (go)

### [`v1.21.6`](https://togithub.com/golang/go/compare/go1.21.5...go1.21.6)

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