golang: v↑ go1.15 (1.15.10 -> 1.15.11)

Going Go1.15.10 -> Go1.15.11 brings in fixes to compiler, runtime and stdlib:

https://golang.org/doc/devel/release.html#go1.15.minor

Tested on helloworld SR (by adjusting it to use go1.15 instead of go1.16).
5 jobs for 1.0
in 0 seconds, using 0 compute credits, and was queued for 0 seconds