Remove buildkite configuration

Author: andreabedini

.github/workflows/pipeline.yml

@@ -233,10 +233,3 @@ jobs:
       - uses: actions/checkout@v3
       - name: "Check hix -- run github:haskell/cabal/3.10#cabal-install:exe:cabal -- --version"
         run: "HIX_DIR=$(mktemp -d) nix run .#hix --accept-flake-config -- run github:haskell/cabal/3.10#cabal-install:exe:cabal --accept-flake-config --override-input haskellNix . -- --version"
-
-  nix-tools-build:
-    runs-on: [self-hosted, linux]
-    steps:
-      - uses: actions/checkout@v3
-      - name: "nix-tools build"
-        run: cd ./nix-tools && .buildkite/nix-tools-build.sh