output-tx.h: include tm-threads.h

Required to properly resolve the types in the header without depending
on includes coming before it in C files.

Ticket: OISF#7227

src/output-tx.h

@@ -26,6 +26,7 @@
 #ifndef SURICATA_OUTPUT_TX_H
 #define SURICATA_OUTPUT_TX_H
 
+#include "tm-threads.h"
 #include "decode.h"
 #include "flow.h"