doc/articles/race_detector: update for Go 1.22 loop variable changes

One of the examples was no longer racy. Change the example
to use a variable declared outside of the loop, to make it racy.

Fixes golang/go#69261

Change-Id: I79d5c9372d4badbdaccdea53e8b395291805dc47
Reviewed-on: https://go-review.googlesource.com/c/website/+/610975
Reviewed-by: Dmitri Shuralyov <[email protected]>
Commit-Queue: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

_content/doc/articles/race_detector.html

@@ -200,7 +200,8 @@ <h3 id="Race_on_loop_counter">Race on loop counter</h3>
 func main() {
 	var wg sync.WaitGroup
 	wg.Add(5)
-	for i := 0; i &lt; 5; i++ {
+	var i int
+	for i = 0; i &lt; 5; i++ {
 		go func() {
 			fmt.Println(i) // Not the 'i' you are looking for.
 			wg.Done()
@@ -221,7 +222,8 @@ <h3 id="Race_on_loop_counter">Race on loop counter</h3>
 func main() {
 	var wg sync.WaitGroup
 	wg.Add(5)
-	for i := 0; i &lt; 5; i++ {
+	var i int
+	for i = 0; i &lt; 5; i++ {
 		go func(j int) {
 			fmt.Println(j) // Good. Read local copy of the loop counter.
 			wg.Done()