Bump containers upper bound

hpc.cabal

@@ -36,7 +36,7 @@ Library
 
     Build-Depends:
         base       >= 4.4.1 && < 4.13,
-        containers >= 0.4.1 && < 0.6,
+        containers >= 0.4.1 && < 0.7,
         directory  >= 1.1   && < 1.4,
         filepath   >= 1     && < 1.5,
         time       >= 1.2   && < 1.9