[go] Update to go1.21
Remove uses of the golang.org/x/exp/slices package, which is now
provided by the stdlib (with a small difference in the signature of the
`SortFunc` function).
Change-Id: I516eaedf8e165a80f023579d264001f819fcec7a
Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/infra/+/904701
Reviewed-by: Anthony Fandrianto <atyfto@google.com>
Fuchsia-Auto-Submit: Oliver Newman <olivernewman@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
8 files changed
