Require hashable >= 1.4 (#506)

Resolves #487.

Author: sjakobi

unordered-containers.cabal

@@ -61,7 +61,7 @@ library
   build-depends:
     base >= 4.10 && < 5,
     deepseq >= 1.4.3,
-    hashable >= 1.2.5 && < 1.6,
+    hashable >= 1.4 && < 1.6,
     template-haskell < 2.24
 
   default-language: Haskell2010