[7.x](backport #25671) Update Go version to 1.16.4

[mergify]

This is an automatic backport of pull request #25671 done by Mergify.
Cherry-pick of 4dc5285 has failed:

On branch mergify/bp/7.x/pr-25671
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 4dc5285ae.
  (fix conflicts and run "git cherry-pick --continue")
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  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .go-version
	modified:   CHANGELOG-developer.next.asciidoc
	modified:   CHANGELOG.next.asciidoc
	modified:   NOTICE.txt
	modified:   auditbeat/Dockerfile
	modified:   dev-tools/mage/crossbuild.go
	modified:   dev-tools/mage/gotest_test.go
	modified:   filebeat/Dockerfile
	modified:   generator/common/beatgen/setup/setup.go
	modified:   go.mod
	modified:   go.sum
	modified:   heartbeat/Dockerfile
	modified:   journalbeat/Dockerfile
	modified:   journalbeat/magefile.go
	modified:   libbeat/Dockerfile
	modified:   metricbeat/Dockerfile
	modified:   metricbeat/module/http/_meta/Dockerfile
	modified:   packetbeat/Dockerfile
	modified:   x-pack/elastic-agent/Dockerfile
	modified:   x-pack/functionbeat/Dockerfile
	modified:   x-pack/libbeat/Dockerfile

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   libbeat/docs/version.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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[elasticmachine]

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Build stats

• Build Cause: michel-laterman commented: /test

• Start Time: 2021-05-28T22:51:46.567+0000

• Duration: 91 min 22 sec

• Commit: baa386f

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❕ Flaky test report

No test was executed to be analysed.

[michel-laterman]

/test

[michel-laterman]

@kvch, are these the same e2e test failures as they were on the PR to master? Is it safe to ignore?

[kvch]

Yes. The error is unrelated to your change.