internal/history: document Go 1.14.6 and 1.13.14
internal/history: document Go 1.14.6 and 1.13.14

Change-Id: I8aa0d04a80a131e928b1e900bf8ea459583e8c28
Reviewed-on: https://go-review.googlesource.com/c/website/+/243120
Reviewed-by: Alexander Rakoczy <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@golang.org>
Run-TryBot: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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