ci: bump webfactory/ssh-agent from 0.8.0 to 0.9.0

Bumps [webfactory/ssh-agent](https://github.com/webfactory/ssh-agent) from 0.8.0 to 0.9.0.
- [Release notes](https://github.com/webfactory/ssh-agent/releases)
- [Changelog](https://github.com/webfactory/ssh-agent/blob/master/CHANGELOG.md)
- [Commits](webfactory/ssh-agent@v0.8.0...v0.9.0)

---
updated-dependencies:
- dependency-name: webfactory/ssh-agent
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yaml

@@ -25,7 +25,7 @@ jobs:
         name: ossystems-lab
         authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
     - name: Install SSH Private Key
-      uses: webfactory/ssh-agent@v0.8.0
+      uses: webfactory/ssh-agent@v0.9.0
       with:
         ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY }}
     - run: nix flake check
@@ -50,7 +50,7 @@ jobs:
         name: ossystems-lab
         authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
     - name: Install SSH Private Key
-      uses: webfactory/ssh-agent@v0.8.0
+      uses: webfactory/ssh-agent@v0.9.0
       with:
         ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY }}
     - run: nix -Lv build ".#nixosConfigurations.${{ matrix.nixosConfiguration }}.config.system.build.toplevel"