github workflow: try to remove version numbers

Author: DavidEGrayson

.github/workflows/ci.yaml

@@ -4,16 +4,16 @@ on:
   push:
 jobs:
   ci:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu
     steps:
     - name: Checkout this repository
-      uses: actions/checkout@v2.3.4
+      uses: actions/checkout
     - name: Cache for arduino-ci
-      uses: actions/cache@v2.1.3
+      uses: actions/cache
       with:
         path: |
           ~/.arduino15
         key: ${{ runner.os }}-arduino
     - name: Install nix
-      uses: cachix/install-nix-action@v12
+      uses: cachix/install-nix-action
     - run: nix-shell -I nixpkgs=channel:nixpkgs-unstable -p arduino-ci --run "arduino-ci"