chore(config): upgrade deprecated config modules

Signed-off-by: Amogh Lele <amogh@dyte.io>

config/config.exs

@@ -5,7 +5,7 @@
 # is restricted to this project.
 
 # General application configuration
-use Mix.Config
+import Config
 
 config :ketbin,
   ecto_repos: [Ketbin.Repo]

config/dev.exs

@@ -1,4 +1,4 @@
-use Mix.Config
+import Config
 
 # For development, we disable any cache and enable
 # debugging and code reloading.