unix: fix typo in test

Change-Id: I80b28a28a9e6133a7c8a9340ce5914498ff6bf0f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/292331
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

unix/syscall_unix_test.go

@@ -122,7 +122,7 @@ func TestSignalNum(t *testing.T) {
 
 func TestFcntlInt(t *testing.T) {
 	t.Parallel()
-	file, err := ioutil.TempFile("", "TestFnctlInt")
+	file, err := ioutil.TempFile("", "TestFcntlInt")
 	if err != nil {
 		t.Fatal(err)
 	}