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.