internal/history: document Go 1.21.3 and 1.20.10 releases

Change-Id: I2b60b5f4129a565d23fd2eb5d64c0dbf578134b4
Reviewed-on: https://go-review.googlesource.com/c/website/+/534217
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

internal/history/release.go

@@ -16,13 +16,11 @@ import "html/template"
 var Releases = []*Release{
 	{
 		Date: Date{2023, 10, 10}, Version: Version{1, 21, 3},
-		Future:   true,
-		Security: &FixSummary{Quantifier: "a", Components: []template.HTML{"the standard library"}},
+		Security: &FixSummary{Quantifier: "a", Packages: []string{"net/http"}},
 	},
 	{
 		Date: Date{2023, 10, 10}, Version: Version{1, 20, 10},
-		Future:   true,
-		Security: &FixSummary{Quantifier: "a", Components: []template.HTML{"the standard library"}},
+		Security: &FixSummary{Quantifier: "a", Packages: []string{"net/http"}},
 	},
 	{
 		Date: Date{2023, 10, 5}, Version: Version{1, 21, 2},