Merge pull request #2350 from tweag/renovate/cachix-install-nix-action-31.x

chore(deps): update cachix/install-nix-action action to v31.8.1

Author: mergify[bot]

.github/workflows/update-ghc.yaml

@@ -22,7 +22,7 @@ jobs:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
           ref: master
-      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31.7.0
+      - uses: cachix/install-nix-action@fd24c48048070c1be9acd18c9d369a83f0fe94d7 # v31.8.1
         with:
           nix_path: nixpkgs=nixpkgs/default.nix
       - name: Fetch updates

.github/workflows/workflow.yaml

@@ -71,7 +71,7 @@ jobs:
         with:
           path: ~/repo-cache
           key: repo-cache-${{ runner.os }}-nixpkgs-${{ env.cache-version }}
-      - uses: cachix/install-nix-action@9280e7aca88deada44c930f1e2c78e21c3ae3edd # v31.7.0
+      - uses: cachix/install-nix-action@fd24c48048070c1be9acd18c9d369a83f0fe94d7 # v31.8.1
         with:
           nix_path: nixpkgs=./nixpkgs/default.nix
           extra_nix_config: |