fix test warnings

Author: lukaszsamson

apps/elixir_ls_debugger/test/fixtures/mix_project/config/config.exs

@@ -1,6 +1,6 @@
 # This file is responsible for configuring your application
 # and its dependencies with the aid of the Mix.Config module.
-use Mix.Config
+import Config
 
 # This configuration is loaded before any dependency and is restricted
 # to this project. If another project depends on this project, this

apps/elixir_ls_utils/config/config.exs

@@ -1,6 +1,6 @@
 # This file is responsible for configuring your application
 # and its dependencies with the aid of the Mix.Config module.
-use Mix.Config
+import Config
 
 # This configuration is loaded before any dependency and is restricted
 # to this project. If another project depends on this project, this

apps/language_server/test/providers/document_symbols_test.exs

@@ -2337,7 +2337,7 @@ defmodule ElixirLS.LanguageServer.Providers.DocumentSymbolsTest do
     uri = "file:///project/test.exs"
 
     text = """
-    use Mix.Config
+    import Config
     config :logger, :console,
        level: :info,
        format: "$date $time [$level] $metadata$message\n",
@@ -2387,7 +2387,7 @@ defmodule ElixirLS.LanguageServer.Providers.DocumentSymbolsTest do
     uri = "file:///project/test.exs"
 
     text = """
-    use Mix.Config
+    import Config
     config :logger, :console,
        level: :info,
        format: "$date $time [$level] $metadata$message\n",