internal/releasetargets: regenerate all ports for Go 1.21

It's a no-op since the only newly added port is wasip1/wasm,
and we won't be making binary releases for it at this time.

For golang/go#40561.
For golang/go#58141.

Change-Id: I0c9932fdfca0842c6860bca0cdbc4b1d64fdefff
Reviewed-on: https://go-review.googlesource.com/c/build/+/503756
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: dmitshur

internal/releasetargets/allports/go1.21.txt

@@ -40,6 +40,7 @@ plan9/386
 plan9/amd64
 plan9/arm
 solaris/amd64
+wasip1/wasm
 windows/386
 windows/amd64
 windows/arm

internal/releasetargets/releasetargets.go

@@ -237,6 +237,7 @@ var unbuildableOSs = map[string]bool{
 	"android": true,
 	"ios":     true,
 	"js":      true,
+	"wasip1":  true,
 }
 
 // TargetsForGo1Point returns the ReleaseTargets that apply to the given