Raise lower bound on bifunctors to match Stackage LTS

servant/servant.cabal

@@ -84,7 +84,7 @@ library
   -- Here can be exceptions if we really need features from the newer versions.
   build-depends:
       base-compat            >= 0.10.4   && < 0.11
-    , bifunctors             >= 5.4      && < 5.6
+    , bifunctors             >= 5.5.3    && < 5.6
     , aeson                  >= 1.3.1.1  && < 1.5
     , attoparsec             >= 0.13.2.2 && < 0.14
     , case-insensitive       >= 1.2.0.11 && < 1.3