ci: Remove cachix nix installer action

This should no longer be required now that
DeterminateSystems/nix-installer-action#68
has been resolved.

Author: jimmidyson

.github/workflows/e2e.yml

@@ -39,19 +39,10 @@ jobs:
         with:
           fetch-depth: 0
 
-      # Install nix using cachix/install-nix-action if running on ARC runners
-      # See: https://github.com/DeterminateSystems/nix-installer-action/issues/68
-      - name: Install Nix on self-hosted ARC runners
-        uses: cachix/install-nix-action@v31
-        if: inputs.runs-on == 'self-hosted-ncn-dind'
-        with:
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Install devbox
         uses: jetify-com/[email protected]
         with:
           enable-cache: ${{ inputs.runs-on != 'self-hosted-ncn-dind' }}
-          skip-nix-installation: ${{ inputs.runs-on == 'self-hosted-ncn-dind' }}
 
       - name: Go cache
         uses: actions/cache@v4