net: fix timeout test bug

This was supposed to be in CL 18205 but I submitted via the web
instead of from my computer, so it got lost.
May deflake some things.

Change-Id: I880fb74b5943b8a17f952a82639c60126701187a
Reviewed-on: https://go-review.googlesource.com/18259Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/timeout_test.go

@@ -996,7 +996,6 @@ func TestReadWriteDeadlineRace(t *testing.T) {
 	if testing.Short() {
 		N = 50
 	}
-	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
 
 	ln, err := newLocalListener("tcp")
 	if err != nil {