chore: Remove cabal.project.non-nix

We don't have any source-repository-package stanzas in there anymore, so there's no
need to keep it around anymore.

.github/scripts/arm/build.sh

@@ -55,7 +55,6 @@ cd ~/$SCRIPT_DIR
 git clone https://github.com/PostgREST/postgrest.git
 cd postgrest
 git checkout $PGRST_GITHUB_COMMIT
-cp cabal.project.non-nix cabal.project
 cabal v2-update && cabal v2-build
 
 # Strip unused symbols from executable

.github/workflows/build.yaml

@@ -164,10 +164,9 @@ jobs:
           ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-vanilla-0.0.8.yaml
           ghcup install ghc ${{ matrix.ghc }}
           ghcup set ghc ${{ matrix.ghc }}
-      - name: Copy cabal.project & fix caching
+      - name: Fix caching
         run: |
           mkdir ~/.cabal
-          cp cabal.project.non-nix cabal.project
       - name: Cache
         uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4
         with: