fix incorrect and misleading help string (Message.dir values; notice that the default value was correct); no functionality change

src/pEp/_pEp/pEpmodule.cc

@@ -414,7 +414,7 @@ namespace pEp {
                                      "\n"
                                      "new p≡p message\n"
                                      "\n"
-                                     "   dir         1 for outgoing, 2 for incoming\n"
+                                     "   dir         0 for incoming, 1 for outgoing\n"
                                      "   from        Identity() of sender\n"
                                      "\n"
                                      "Message(mime_text)\n"