haskell-cabal-bounds: use versionOlder

for some reason, versionAtLeast doesn't work

Changed files
+1 -1
pkgs
+1 -1
pkgs/top-level/haskell-packages.nix
···
cabalDelete = callPackage ../development/tools/haskell/cabal-delete {};
cabalBounds = callPackage ../development/tools/haskell/cabal-bounds {
-
Cabal = if pkgs.stdenv.lib.versionAtLeast "7.8" ghc.version
+
Cabal = if pkgs.stdenv.lib.versionOlder "7.7" ghc.version
then null
else self.Cabal_1_18_1_3;
};