Fix build with mtl^>=2.3

[jorisdral]

Apparently, without constraints the lib will pick mtl-2.2 on ghc-2.8. However, if we force the use of mtl-2.3, then we get compilation failures. This PR fixes those failures

$ cabal freeze --with-compiler="ghc-9.2.8"
$ cabal freeze --with-compiler="ghc-9.2.8" --constraint="mtl^>=2.3"

diff --git a/cabal.project.freeze b/cabal.project.freeze
index c11278a..443478a 100644
--- a/cabal.project.freeze
+++ b/cabal.project.freeze
@@ -15,14 +15,15 @@ constraints: any.QuickCheck ==2.14.3,
              any.data-array-byte ==0.1.0.1,
              any.deepseq ==1.4.6.1,
              any.directory ==1.3.6.2,
-             any.exceptions ==0.10.4,
+             any.exceptions ==0.10.7,
+             exceptions +transformers-0-4,
              any.filepath ==1.4.2.2,
              any.ghc-bignum ==1.2,
              any.ghc-boot-th ==9.2.8,
              any.ghc-prim ==0.8.0,
              any.hashable ==1.4.3.0,
              hashable +integer-gmp -random-initial-seed,
-             any.mtl ==2.2.2,
+             any.mtl ==2.3.1,
              any.optparse-applicative ==0.18.1.0,
              optparse-applicative +process,
              any.pretty ==1.1.3.6,