chore: update esockd version to fix ssl:getstat/2 for dtls connection

rebar.config

@@ -6,7 +6,7 @@
  [{gproc, {git, "https://github.com/uwiger/gproc", {tag, "0.8.0"}}},
   {jiffy, {git, "https://github.com/emqx/jiffy", {tag, "1.0.5"}}},
   {cowboy, {git, "https://github.com/emqx/cowboy", {tag, "2.7.1"}}},
-  {esockd, {git, "https://github.com/emqx/esockd", {tag, "5.7.2"}}},
+  {esockd, {git, "https://github.com/emqx/esockd", {tag, "5.7.3"}}},
   {ekka, {git, "https://github.com/emqx/ekka", {tag, "0.7.4"}}},
   {gen_rpc, {git, "https://github.com/emqx/gen_rpc", {tag, "2.5.0"}}},
   {cuttlefish, {git, "https://github.com/emqx/cuttlefish", {tag, "v3.0.0"}}}