internal/history: update planned date for Go 1.18.1 and 1.17.9

Change-Id: I8fe625db6f90e407d7803e1ca73980905ab9ace1
Reviewed-on: https://go-review.googlesource.com/c/website/+/398795
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
diff --git a/internal/history/release.go b/internal/history/release.go
index 1d08471..e36dbcf 100644
--- a/internal/history/release.go
+++ b/internal/history/release.go
@@ -15,12 +15,12 @@
 // The table is sorted by date, breaking ties with newer versions first.
 var Releases = []*Release{
 	{
-		Date: Date{2022, 4, 7}, Version: Version{1, 18, 1},
+		Date: Date{2022, 4, 12}, Version: Version{1, 18, 1},
 		Future:   true,
 		Security: &FixSummary{Quantifier: "a", Components: []template.HTML{"the standard library"}},
 	},
 	{
-		Date: Date{2022, 4, 7}, Version: Version{1, 17, 9},
+		Date: Date{2022, 4, 12}, Version: Version{1, 17, 9},
 		Future:   true,
 		Security: &FixSummary{Quantifier: "a", Components: []template.HTML{"the standard library"}},
 	},