Fix index-state syntax in cabal.project

index-state stanza in cabal.project is "last wins", so 
```
index-state: 2022-12-24T00:00:00Z
index-state: cardano-haskell-packages 2022-11-02T15:34:17Z
``` would set the index state of hackage to HEAD.
The correct syntax to set the index-state of both repositories is
```
index-state:
  , hackage.haskell.org 2022-12-24T00:00:00Z
  , cardano-haskell-packages 2022-11-02T15:34:17Z
```
haskell.nix has trouble parsing the index-state syntax with multiple repositories, so we repeat the index-state for Hackage. Cabal will ignore the first index-state stanza anyway.

cabal.project

@@ -12,10 +12,14 @@ repository cardano-haskell-packages
 
 -- See CONTRIBUTING for some Nix commands you will need to run if you
 -- update either of these.
--- Bump this if you need newer packages from Hackage
+-- NOTE: repeating the index-state for Hackage is a temporary workaround
+-- for hackage.nix limited parsing ability.
+-- Bump both the following dates if you need newer packages from Hackage
 index-state: 2022-12-24T00:00:00Z
+index-state:
+  , hackage.haskell.org 2022-12-24T00:00:00Z
 -- Bump this if you need newer packages from CHaP
-index-state: cardano-haskell-packages 2022-11-02T15:34:17Z
+  , cardano-haskell-packages 2022-11-02T15:34:17Z
 
 packages:
   eras/allegra/impl