golang: v↑ go1.16 (1.16.4 -> 1.16.8)

Going Go1.16.4 -> Go1.16.8 brings in fixes to compiler, runtime and stdlib
including security fixes to net, crypto/tls, archive/zip, math/big, and
net/http/httputil packages:

https://golang.org/doc/devel/release.html#go1.16.minor

Tested on helloworld SR.