Bump base to < 4.21

process.cabal

@@ -86,7 +86,7 @@ library
 
     ghc-options: -Wall
 
-    build-depends: base      >= 4.10 && < 4.20,
+    build-depends: base      >= 4.10 && < 4.21,
                    directory >= 1.1 && < 1.4,
                    filepath  >= 1.2 && < 1.6,
                    deepseq   >= 1.1 && < 1.6