cmd/compile: remove loop variable capture workarounds

Since Go 1.22, loop variables have per-iteration scope, making
the x := x this pattern unnecessary for goroutine capture.

No issue required for this trivial cleanup.

Change-Id: I00d98522537fc2b9a6b4d598c8aa21b447628d41
Reviewed-on: https://go-review.googlesource.com/c/go/+/753400
Auto-Submit: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

src/cmd/compile/internal/noder/noder.go

@@ -41,7 +41,6 @@ func LoadPackage(filenames []string) {
 	// Move the entire syntax processing logic into a separate goroutine to avoid blocking on the "sem".
 	go func() {
 		for i, filename := range filenames {
-			filename := filename
 			p := noders[i]
 			sem <- struct{}{}
 			go func() {

src/cmd/compile/internal/ssa/_gen/main.go

@@ -184,7 +184,6 @@ func main() {
 	}
 	var wg sync.WaitGroup
 	for _, task := range tasks {
-		task := task
 		wg.Add(1)
 		go func() {
 			task()