add newlines to end of the default configs (#5256)

docs/sample_config/default_config.nu

@@ -332,4 +332,4 @@ let-env config = {
       event: { send: menu name: commands_with_description }
     }
   ]
-}
+}

docs/sample_config/default_env.nu

@@ -55,4 +55,4 @@ let-env NU_PLUGIN_DIRS = [
 ]
 
 # To add entries to PATH (on Windows you might use Path), you can use the following pattern:
-# let-env PATH = ($env.PATH | prepend '/some/path')
+# let-env PATH = ($env.PATH | prepend '/some/path')