Bump awalsh128/cache-apt-pkgs-action from 1.4.2 to 1.6.0

Bumps [awalsh128/cache-apt-pkgs-action](https://github.com/awalsh128/cache-apt-pkgs-action) from 1.4.2 to 1.6.0.
- [Release notes](https://github.com/awalsh128/cache-apt-pkgs-action/releases)
- [Commits](awalsh128/cache-apt-pkgs-action@v1.4.2...v1.6.0)

---
updated-dependencies:
- dependency-name: awalsh128/cache-apt-pkgs-action
  dependency-version: 1.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/backend-tests.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       -
         name: Install libreoffice
-        uses: awalsh128/cache-apt-pkgs-action@v1.4.2
+        uses: awalsh128/cache-apt-pkgs-action@v1.6.0
         with:
           packages: libreoffice libreoffice-pdfimport
           version: 1.0