qualify invokelatest for Julia < 1.9

`invokelatest` was not exported in Julia versions prior to 1.9. Qualify the use to be compatible to older versions.

Author: tanmaykm

src/client.jl

@@ -165,9 +165,9 @@ function subscription_loop(conn::SubscriptionConnection, err_callback::Function)
             reply = convert_reply(reply)
             message = SubscriptionMessage(reply)
             if message.message_type == SubscriptionMessageType.Message
-                invokelatest(conn.callbacks[message.channel], message)
+                Base.invokelatest(conn.callbacks[message.channel], message)
             elseif message.message_type == SubscriptionMessageType.Pmessage
-                invokelatest(conn.pcallbacks[message.channel], message)
+                Base.invokelatest(conn.pcallbacks[message.channel], message)
             end
         catch err
             err_callback(err)