Tweaks to pgf2.cabal

src/runtime/haskell/pgf2.cabal

@@ -30,9 +30,9 @@ library
     PGF2.Expr,
     PGF2.Type
   build-depends:
-    base >= 4.3, -- >= 4.9.1 && < 4.15,
-    containers, -- >= 0.5.7 && < 0.7,
-    pretty, -- >= 1.1.3 && < 1.2,
+    base >= 4.3 && < 4.15,
+    containers,
+    pretty,
     array,
     random
   default-language: Haskell2010
@@ -48,4 +48,4 @@ test-suite basic
   build-depends:
     base,
     HUnit,
-    pgf2 >= 2.0.0
+    pgf2