[release-branch.go1.21] go1.21.6

Change-Id: I85e48d54e6938b3882a0bb8f2de75fee6ecb2668
Reviewed-on: https://go-review.googlesource.com/c/go/+/554839


Commit-Queue: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
TryBot-Bypass: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

VERSION

-go1.21.5
-time 2023-11-29T21:21:46Z
+go1.21.6
+time 2024-01-04T23:43:26Z