Fix ghc-9.12 nix build
This fixes builds for the dependencies haskell-language-server and
proto-lens.
proto-lens fails with:
Error: [Cabal-6661]
filepath wildcard 'proto-lens-imports/google/protobuf/descriptor.proto'
refers to the directory 'proto-lens-imports/google/protobuf', which does not exist or is not a directory.
filepath wildcard 'proto-lens-imports/google/protobuf/descriptor.proto'
does not match any files.
However, SRP is currently required because the released version does not
support ghc-9.12.
The previous haskell-language-server did not support ghc-9.12, so we are
upgrading it to the latest version