internal/history: document Go 1.14.4 and Go 1.13.12
internal/history: document Go 1.14.4 and Go 1.13.12

For golang/go#39347.
For golang/go#39346.

Change-Id: Ied6e4f226f1855566ea83bbe64a76a3268870adf
Reviewed-on: https://go-review.googlesource.com/c/website/+/235921
Run-TryBot: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

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