fix: upgrade to emqtt 1.13.4

[zmstone]

emqtt 1.13.4 has reconnect fixed
now bench clients should experience less shutdowns when testing with higher connection rate than the target broker allows.

when test against emqx with max_conn_rate set to 10

> ./_build/emqtt_bench/rel/emqtt_bench/bin/emqtt_bench conn -h localhost -p 1883 -c 1000 --reconnect 100000
Start with 20 workers, addrs pool size: 1 and req interval: 200 ms

1s connect_succ total=18 rate=17.96/sec
2s connect_succ total=28 rate=10.00/sec
3s connect_succ total=38 rate=10.00/sec
4s connect_succ total=48 rate=10.00/sec
5s connect_succ total=57 rate=9.00/sec
6s connect_succ total=67 rate=10.00/sec
7s connect_succ total=77 rate=10.00/sec
8s connect_succ total=87 rate=10.00/sec
9s connect_succ total=97 rate=10.00/sec
10s connect_succ total=107 rate=10.00/sec
11s connect_succ total=117 rate=10.00/sec
12s connect_succ total=127 rate=10.00/sec
13s connect_succ total=137 rate=10.00/sec
14s connect_succ total=147 rate=10.00/sec
15s connect_succ total=157 rate=10.00/sec