Remove unnecessary language extensions

Attempting to abide by the Principle of Least Power. Also: the smaller the
headers in each module are, the happier I am.

src/App.hs

@@ -1,10 +1,5 @@
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
 --------------------------------------------------------------------------------
 module App where
 --------------------------------------------------------------------------------