go2-language-changes: update generics reference
go2-language-changes: update generics reference

Change-Id: I73cd7f2549d5d4dbe6f55fef5620b72f9c65059e
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/350849
Reviewed-by: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Trust: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>

golang/proposal,golang/proposal