[7.17](backport #36000) upgrade Go to 1.20.6

[mergify]

This is an automatic backport of pull request #36000 done by Mergify.
Cherry-pick of a278734 has failed:

On branch mergify/bp/7.17/pr-36000
Your branch is up to date with 'origin/7.17'.

You are currently cherry-picking commit a278734f11.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.next.asciidoc
	modified:   dev-tools/mage/gotest_test.go
	modified:   filebeat/input/syslog/format_check.go
	modified:   filebeat/input/syslog/rfc3164_parser.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   .go-version
	both modified:   .golangci.yml
	both modified:   Vagrantfile
	both modified:   auditbeat/Dockerfile
	deleted by us:   dev-tools/kubernetes/filebeat/Dockerfile.debug
	deleted by us:   dev-tools/kubernetes/heartbeat/Dockerfile.debug
	deleted by us:   dev-tools/kubernetes/metricbeat/Dockerfile.debug
	both modified:   dev-tools/mage/gotest.go
	both modified:   filebeat/input/syslog/rfc5424_parser.go
	both modified:   heartbeat/Dockerfile
	both modified:   libbeat/docs/version.asciidoc
	deleted by us:   libbeat/reader/syslog/rfc3164_test.go
	deleted by us:   libbeat/reader/syslog/rfc5424_test.go
	both modified:   metricbeat/Dockerfile
	both modified:   metricbeat/module/http/_meta/Dockerfile
	both modified:   metricbeat/module/nats/_meta/Dockerfile
	both modified:   packetbeat/Dockerfile
	both modified:   x-pack/functionbeat/Dockerfile
	both modified:   x-pack/metricbeat/module/stan/_meta/Dockerfile

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[elasticmachine]

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• Start Time: 2023-10-23T19:54:44.400+0000

• Duration: 175 min 11 sec

Test stats 🧪

Test	Results
Failed	0
Passed	22161
Skipped	1402
Total	23563

💚 Flaky test report

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[mergify]

This pull request has not been merged yet. Could you please review and merge it @AndersonQ? 🙏