add new string to deltachat.h

deltachat-ffi/deltachat.h

@@ -4427,7 +4427,8 @@ void dc_event_unref(dc_event_t* event);
 #define DC_STR_DEVICE_MESSAGES_HINT       70
 #define DC_STR_WELCOME_MESSAGE            71
 #define DC_STR_UNKNOWN_SENDER_FOR_CHAT    72
-#define DC_STR_COUNT                      72
+#define DC_STR_SUBJECT_FOR_NEW_CONTACT    73
+#define DC_STR_COUNT                      73
 
 /*
  * @}