[release-branch.go1.22] spec: fix typo in year (it's 2024 now)

[release-branch.go1.22] spec: fix typo in year (it's 2024 now)

While at it, set the date to the Go 1.22 release date.

Change-Id: I03872626e500433eb63786d24c67810c8c6289f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/562337
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/562320
Reviewed-by: Russ Cox <rsc@golang.org>