chore: bump emqx_gateway_coap version

apps/emqx_gateway_coap/src/emqx_gateway_coap.app.src

@@ -1,7 +1,7 @@
 %% -*- mode: erlang -*-
 {application, emqx_gateway_coap, [
     {description, "CoAP Gateway"},
-    {vsn, "0.1.5"},
+    {vsn, "0.1.6"},
     {registered, []},
     {applications, [kernel, stdlib, emqx, emqx_gateway]},
     {env, []},