golang: v↑ go1.16 (1.16.10 -> 1.16.13)

Going Go1.16.10 -> Go1.16.13 brings in fixes to compiler, runtime and stdlib
including security fixes to syscall and net/http packages.

https://go.dev/doc/devel/release#go1.16.minor

Tested manually via adjusted helloworld because nothing intree currently uses Go1.16.
9 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed Cloudooo.UnitTest-Master

00:16:44

passed SlapOS.Eggs.UnitTest-Master.Python2

00:18:50

passed SlapOS.Eggs.UnitTest-Master.Python3

00:15:58

passed SlapOS.SlapRunner.ResilienceTest-Master

00:25:17

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

01:39:23

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

04:21:53

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

20:23:03

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

08:19:52

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

08:57:39