internal/history: document Go 1.19.1 and 1.18.6 releases
internal/history: document Go 1.19.1 and 1.18.6 releases

Change-Id: Ib52c14f6248667fcd3440c698fc201ecee995e6f
Reviewed-on: https://go-review.googlesource.com/c/website/+/428617
Run-TryBot: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Carlos Amedee <ab5e2bca84933118bbc9d48ffaccce3bac4eeb64@golang.org>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website