Github actions: Clean up superflous test.yml file

.github/workflows/test.yml

@@ -1,20 +0,0 @@
-name: Test
-
-on:
-  pull_request:
-    paths-ignore:
-    - '**.md'
-  push:
-    paths-ignore:
-    - '**.md'
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-    env:
-      NIX_PATH: "nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz"
-    steps:
-    - uses: cachix/install-nix-action@v12
-    - uses: actions/checkout@v1
-    - run: |
-      make -C tests