[release-branch.go1.21] go1.21.0

Change-Id: Iffac2ce43cd3a48ba420594adc3eab5aa9bcf113
Reviewed-on: https://go-review.googlesource.com/c/go/+/517055


Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>

VERSION

-go1.21rc4
-time 2023-08-01T22:09:51Z
+go1.21.0
+time 2023-08-04T20:14:06Z