net: correct TestIPConnSpecificMethods comment after CL 476217

As suggested by Cherry in
https://go-review.googlesource.com/c/go/+/476217/5/src/net/protoconn_test.go#171

Change-Id: I4ce3c034b44953720c543a87639fd173f86af7dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/476535
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/net/protoconn_test.go

@@ -168,7 +168,8 @@ func TestIPConnSpecificMethods(t *testing.T) {
 	}
 	c, err := ListenIP("ip4:icmp", la)
 	if testenv.SyscallIsNotSupported(err) {
-		// May be inside a container that disallows creating a socket.
+		// May be inside a container that disallows creating a socket or
+		// not running as root.
 		t.Skipf("skipping: %v", err)
 	} else if err != nil {
 		t.Fatal(err)