perf(pool): change emqx_connector default pool type to hash

apps/emqx_connector/src/emqx_connector_http.erl

@@ -105,7 +105,7 @@ retry_interval(default) -> <<"1s">>;
 retry_interval(_) -> undefined.
 
 pool_type(type) -> pool_type();
-pool_type(default) -> random;
+pool_type(default) -> hash;
 pool_type(_) -> undefined.
 
 pool_size(type) -> non_neg_integer();