fix(mix): fix `lhttpc` version specification

mix.exs

@@ -193,7 +193,7 @@ defmodule EMQXUmbrella.MixProject do
       {:erlcloud, github: "emqx/erlcloud", tag: "3.5.16-emqx-1", override: true},
       # erlcloud's rebar.config requires rebar3 and does not support Mix,
       # so it tries to fetch deps from git. We need to override this.
-      {:lhttpc, tag: "1.6.2", override: true},
+      {:lhttpc, "1.6.2", override: true},
       {:eini, "1.2.9", override: true},
       {:base16, "1.0.0", override: true},
       # end of erlcloud's deps