Revert "add subcommand lint_haskell to lint haskell code"

This reverts commit 27e3033b3b.

Makefile

@@ -14,7 +14,6 @@ usage:
 	@echo "  format_haskell -- Format haskell stuff, including source code and cabal files"
 	@echo "  format_nix -- Format *.nix files only"
 	@echo "  format_check -- Check if all haskell stuff have been formatted correctly"
-	@echo "  lint_haskell -- run hlint on all haskell files"
 
 hoogle:
 	pkill hoogle || true
@@ -38,9 +37,6 @@ format_check:
 	     -not -path './haddock/*' \
 	  | xargs fourmolu $(FORMAT_EXTENSIONS) -m check
 
-lint_haskell:
-	find -name '*.hs' -not -path './dist*/*' -not -path './haddock/*' | xargs hlint
-
 haddock:
 	cabal haddock --haddock-html --haddock-hoogle --builddir=haddock