Allow tar-0.6 in serialise benchmarks

serialise/serialise.cabal

@@ -269,7 +269,7 @@ benchmark versus
     aeson                   >= 0.7     && < 2.3,
     cereal                  >= 0.5.2.0 && < 0.6,
     half                    >= 0.2.2.3 && < 0.4,
-    tar                     >= 0.4     && < 0.6,
+    tar                     >= 0.4     && < 0.7,
     zlib                    >= 0.5     && < 0.7,
     pretty                  >= 1.0     && < 1.2,
     criterion               >= 1.0     && < 1.7,