Use head.hackage only for GHC < 9.13 (we need to update this each time there is a release...)

Might fix #195

Author: angerman

tool-map.nix

@@ -17,7 +17,7 @@ let
              7541f32a4ccca4f97aea3b22f5e593ba2c0267546016b992dfadcd2fe944e55d
           --sha256: sha256-aVI93DtHziicNn2mGli0YE+bC5BeT7mOQQETp2Thi68=
 
-        if impl(ghc < 9.11)
+        if impl(ghc < 9.13)
           active-repositories: hackage.haskell.org
         else
           active-repositories: hackage.haskell.org, head.hackage.ghc.haskell.org