Bump filepath upper bound to <1.6 (#187)

haskeline.cabal

@@ -65,7 +65,7 @@ Library
     -- wasn't fixed until 7.4.1
     Build-depends: base >=4.9 && < 4.20, containers>=0.4 && < 0.8,
                    directory>=1.1 && < 1.4, bytestring>=0.9 && < 0.13,
-                   filepath >= 1.2 && < 1.5, transformers >= 0.2 && < 0.7,
+                   filepath >= 1.2 && < 1.6, transformers >= 0.2 && < 0.7,
                    process >= 1.0 && < 1.7, stm >= 2.4 && < 2.6,
                    exceptions == 0.10.*
     Default-Language: Haskell98