doc: fix typo in spec example code comment

R=r, golang-dev, adg
CC=golang-dev
https://golang.org/cl/5308071

doc/go_spec.html

@@ -4851,7 +4851,7 @@ run-time panics raised by <code>g</code>.
 <pre>
 func protect(g func()) {
 	defer func() {
-		log.Println("done")  // Println executes normally even in there is a panic
+		log.Println("done")  // Println executes normally even if there is a panic
 		if x := recover(); x != nil {
 			log.Printf("run time panic: %v", x)
 		}