fix(ci): add `ra` to emqx app dependencies as well

apps/emqx/rebar.config

@@ -34,7 +34,8 @@
     {emqx_http_lib, {git, "https://github.com/emqx/emqx_http_lib.git", {tag, "0.5.3"}}},
     {pbkdf2, {git, "https://github.com/emqx/erlang-pbkdf2.git", {tag, "2.0.4"}}},
     {recon, {git, "https://github.com/ferd/recon", {tag, "2.5.1"}}},
-    {snabbkaffe, {git, "https://github.com/kafka4beam/snabbkaffe.git", {tag, "1.0.8"}}}
+    {snabbkaffe, {git, "https://github.com/kafka4beam/snabbkaffe.git", {tag, "1.0.8"}}},
+    {ra, "2.7.3"}
 ]}.
 
 {plugins, [{rebar3_proper, "0.12.1"}, rebar3_path_deps]}.