doc/go_mem.html: correct the channel example

While we're here, also fix two HTML issues.

Fixes #9235.

Change-Id: I6e2f50931c0f387881271484a726ac2308518cf4
Reviewed-on: https://go-review.googlesource.com/7602Reviewed-by: Rob Pike <r@golang.org>

doc/go_mem.html

@@ -322,11 +322,11 @@ var limit = make(chan int, 3)
 
 func main() {
 	for _, w := range work {
-		go func() {
-			limit <- 1
+		go func(w func()) {
+			limit &lt;- 1
 			w()
-			<-limit
-		}()
+			&lt;-limit
+		}(w)
 	}
 	select{}
 }