Allow building with containers-0.7.*

linear.cabal

@@ -55,7 +55,7 @@ library
     binary               >= 0.5   && < 0.9,
     bytes                >= 0.15  && < 1,
     cereal               >= 0.4.1.1 && < 0.6,
-    containers           >= 0.4   && < 0.7,
+    containers           >= 0.4   && < 0.8,
     deepseq              >= 1.1   && < 1.6,
     distributive         >= 0.5.1 && < 1,
     ghc-prim,