[updatecli] Bump Golang version to 1.21.7

[github-actions]

What

Bump go release version with the latest release.

Further details

See changelog for 1.21.7
Generated automatically with https://github.com/elastic/elastic-agent-autodiscover/actions/runs/7857106506

---

Bump golang-version to latest version

Update .go-version

1 file(s) updated with "1.21.7": * .go-version

1.21.7

no GitHub Release found for go1.21.7 on "https://github.com/golang/go"

Update .golangci.yml

1 file(s) updated with "1.21.7": * .golangci.yml

1.21.7

no GitHub Release found for go1.21.7 on "https://github.com/golang/go"

---

Created automatically by Updatecli Options: Most of Updatecli configuration is done via its manifest(s). If you close this pull request, Updatecli will automatically reopen it, the next time it runs. If you close this pull request and delete the base branch, Updatecli will automatically recreate it, erasing all previous commits made. Feel free to report any issues at github.com/updatecli/updatecli. If you find this tool useful, do not hesitate to star our GitHub repository as a sign of appreciation, and/or to tell us directly on our chat!