[7.x](backport #26186) Update go version to 1.16.5

[mergify]

This is an automatic backport of pull request #26186 done by Mergify.
Cherry-pick of 881c512 has failed:

On branch mergify/bp/7.x/pr-26186
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 881c51231.
  (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:   auditbeat/Dockerfile
	modified:   filebeat/Dockerfile
	modified:   generator/common/Makefile
	modified:   heartbeat/Dockerfile
	modified:   journalbeat/Dockerfile
	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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[botelastic]

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[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: michel-laterman commented: /test

• Start Time: 2021-06-14T23:36:43.305+0000

• Duration: 80 min 44 sec

• Commit: ba5b526

Test stats 🧪

Test	Results
Failed	0
Passed	1611
Skipped	421
Total	2032

Trends 🧪

💚 Flaky test report

Tests succeeded.

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Test stats 🧪

Test	Results
Failed	0
Passed	1611
Skipped	421
Total	2032

[michel-laterman]

/test

[ChrsMark]

Merging this one so as to try with a new build.