Update GitHub Actions

Author: shajra

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     continue-on-error: true
     steps:
     - uses: actions/checkout@v2
-    - uses: cachix/install-nix-action@v13
+    - uses: cachix/install-nix-action@v14
       with:
         extra_nix_config: |
           trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
@@ -56,7 +56,7 @@ jobs:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: cachix/install-nix-action@v13
+    - uses: cachix/install-nix-action@v14
       with:
         extra_nix_config: |
           trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=