Switch monad-unlift to extra-dep in ghc 8 config

stack-8.0.yaml

@@ -23,6 +23,7 @@ extra-deps:
 - unix-2.7.2.0
 - persistent-template-2.5.1
 - persistent-2.5
+- monad-unlift-0.1.2.0
 packages:
 - .
 # https://github.com/ekmett/either/issues/44
@@ -44,8 +45,4 @@ packages:
     git: https://github.com/mgsloan/hpack
     commit: e7b53c8
   extra-dep: true
-- location:
-    git: https://github.com/fpco/monad-unlift
-    commit: bf6fb29
-  extra-dep: true
 allow-newer: true