doc/go1.21: document macOS and Windows requirements
For #58645.
Fixes #57125.
Fixes #57003.
Fixes #57004.
Change-Id: I365929ca36aeb32e9ecd19f870e70869933ba6a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/500239 Reviewed-by: Eli Bendersky <eliben@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Bypass: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Carlos Amedee <carlos@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>