detect/flowbits: align pointer in the struct

Makes leak sanitizer work without adding LSAN_OPTIONS=use_unaligned=1

Otherwise, leak sanitizer may report rule_id as leaked
when it is still owned by some global variable

src/detect-flowbits.c

@@ -1033,10 +1033,10 @@ static bool PrefilterFlowbitIsPrefilterable(const Signature *s)
 /** core flowbit data structure: map a flowbit id to the signatures that need inspecting after it is
  * found. Part of a rb-tree. */
 typedef struct PrefilterFlowbit {
+    uint32_t *rule_id;     /**< array of signature iid that are part of this prefilter */
     uint32_t id;           /**< flowbit id */
     uint32_t rule_id_size; /**< size in elements of `rule_id` */
     uint32_t rule_id_cnt;  /**< usage in elements of `rule_id` */
-    uint32_t *rule_id;     /**< array of signature iid that are part of this prefilter */
     RB_ENTRY(PrefilterFlowbit) __attribute__((__packed__)) rb;
 } __attribute__((__packed__)) PrefilterFlowbit;