[ci] bump to 2.32.0 (released yesterday) and add it to the cache key

Signed-off-by: Oriol Muñoz <oriol.munoz@digitalasset.com>

Author: OriolMunoz-da

.github/actions/nix/setup_nix/action.yml

@@ -38,11 +38,14 @@ runs:
       shell: bash
       run: |
         set -euxo pipefail
+        NIX_BINARY_VERSION=2.32.0
+        echo "NIX_BINARY_VERSION=$NIX_BINARY_VERSION" >> $GITHUB_ENV
         cat nix/canton-sources.json
         git ls-files nix/ | grep -v '[.]md$' | LC_ALL=C sort | xargs sha256sum -b > /tmp/nix-cache-key
         uname -m >> /tmp/nix-cache-key # Add architecture to the cache key
         echo "gh_cache_version: ${{ inputs.cache_version }}" >> /tmp/nix-cache-key # Add cache version to the cache key
         echo "home: $HOME" >> /tmp/nix-cache-key # important when restoring simlinks from cache, apparently
+        echo "nix binary version: $NIX_BINARY_VERSION" >> /tmp/nix-cache-key # important when restoring simlinks from cache, apparently
         if [ "${{ inputs.oss_only }}" == true ]; then
           echo "Using OSS only dependencies"
           echo "oss_only: ${{ inputs.oss_only }}" >> /tmp/nix-cache-key
@@ -130,7 +133,7 @@ runs:
           fi
           mkdir -p /nix/store
           env
-          sh <(curl -fsSL --retry 8 https://releases.nixos.org/nix/nix-2.14.1/install) --no-daemon
+          sh <(curl -fsSL --retry 8 "https://releases.nixos.org/nix/nix-$NIX_BINARY_VERSION/install") --no-daemon
           sudo mkdir -p /etc/nix
           sudo chmod a+rw /etc/nix
           if [[ "${{ inputs.oss_only }}" == true ]]; then