Fix memory leak in generateAuthenticationResp

> Direct leak of 16 byte(s) in 1 object(s) allocated from:
    >0 0x7ffff74b4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
    >1 0x55555818ef1c in generateAuthenticationResp /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:588
    >2 0x5555581b0fca in nas_nrue /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1405
    >3 0x5555581a3069 in nas_nrue_task /home/guido/repo/openairinterface5g/fix-ue-memory-leaks/openair3/NAS/NR_UE/nr_nas_msg_sim.c:1213
    >4 0x7ffff5e94ac2 in start_thread nptl/pthread_create.c:442

openair3/NAS/NR_UE/nr_nas_msg_sim.c

@@ -614,6 +614,8 @@ static void generateAuthenticationResp(nr_ue_nas_t *nas, as_nas_info_t *initialN
   initialNasMsg->data = (Byte_t *)malloc(size * sizeof(Byte_t));
 
   initialNasMsg->length = mm_msg_encode(mm_msg, (uint8_t *)(initialNasMsg->data), size);
+  // Free res value after encode
+  free(res.value);
 }
 
 int nas_itti_kgnb_refresh_req(instance_t instance, const uint8_t kgnb[32])