net/http: Update server idleTimeout documentation

Fixes #20383

Change-Id: I11234393c3beb669f87976a4f0b424bec7372b82
Reviewed-on: https://go-review.googlesource.com/46434Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/server.go

@@ -2360,7 +2360,7 @@ type Server struct {
 	// IdleTimeout is the maximum amount of time to wait for the
 	// next request when keep-alives are enabled. If IdleTimeout
 	// is zero, the value of ReadTimeout is used. If both are
-	// zero, there is no timeout.
+	// zero, ReadHeaderTimeout is used.
 	IdleTimeout time.Duration
 
 	// MaxHeaderBytes controls the maximum number of bytes the