Use patched version of package fgl.

Fixes:
```
Data/Graph/Inductive/Monad.hs:23:1: error: [GHC-87897]
    • Exception when trying to run compile-time code:
        External interpreter terminated (-15)
    • In the annotation:
        {-# ANN module "HLint: ignore Redundant lambda" #-}
   |
23 | {-# ANN module "HLint: ignore Redundant lambda" #-}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[10 of 29] Compiling Data.Graph.Inductive.NodeMap ( Data/Graph/Inductive/NodeMap.hs, dist/build/Data/Graph/Inductive/NodeMap.o )
[11 of 29] Compiling Data.Graph.Inductive.PatriciaTree ( Data/Graph/Inductive/PatriciaTree.hs, dist/build/Data/Graph/Inductive/PatriciaTree.o )
```

cabal.project

@@ -168,6 +168,12 @@ source-repository-package
 
 --------------------------------------------------------------------------------
 
+source-repository-package
+    type: git
+    location: https://github.com/jonathanknowles/fgl.git
+    tag: d55661c79ca0bb451d7dc7e8d8b99d4f80108c10
+    --sha256: 0kkw3w37bxwaam9ynmvf4z315ms99ddbmz45k2wlnpq2dp7dha50
+
 source-repository-package
     type: git
     location: https://github.com/jonathanknowles/wai.git