counters: remove unused id var in local stats counter

Ticket: #5613.

src/counters.c

@@ -1235,7 +1235,6 @@ static int StatsGetCounterArrayRange(uint16_t s_id, uint16_t e_id,
     i = 1;
     while ((pc != NULL) && (pc->id <= e_id)) {
         pca->head[i].pc = pc;
-        pca->head[i].id = pc->id;
         pc = pc->next;
         i++;
     }

src/counters.h

@@ -95,9 +95,6 @@ typedef struct StatsLocalCounter_ {
     /* pointer to the counter that corresponds to this local counter */
     StatsCounter *pc;
 
-    /* local counter id of the above counter */
-    uint16_t id;
-
     /* total value of the adds/increments, or exact value in case of 'set' */
     int64_t value;