detect: cleanup, remove unused order_id

No longer used, so remove.

src/decode.h

@@ -255,7 +255,6 @@ typedef uint16_t Port;
  * found in this packet */
 typedef struct PacketAlert_ {
     SigIntId num; /* Internal num, used for sorting */
-    SigIntId order_id; /* Internal num, used for sorting */
     uint8_t action; /* Internal num, used for sorting */
     uint8_t flags;
     struct Signature_ *s;

src/detect-engine-alert.c

@@ -46,7 +46,6 @@ void PacketAlertTagInit(void)
 
     memset(&g_tag_pa, 0x00, sizeof(g_tag_pa));
 
-    g_tag_pa.order_id = 1000;
     g_tag_pa.action = ACTION_ALERT;
     g_tag_pa.s = &g_tag_signature;
 }