Remove magic-nix-cache (#2384)

See https://determinate.systems/posts/magic-nix-cache-free-tier-eol/

Author: niklasmohrin

.github/setup_evap/action.yml

@@ -19,7 +19,6 @@ runs:
   using: "composite"
   steps:
     - uses: DeterminateSystems/nix-installer-action@main
-    - uses: DeterminateSystems/magic-nix-cache-action@main
     - uses: nicknovitski/nix-develop@v1
       with:
         arguments: "${{ inputs.shell }}"