Bump actions/cache from 2 to 4

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v2...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/main.yml

@@ -38,7 +38,7 @@ jobs:
           sudo apt-get install -y texlive-fonts-recommended || true
 
       - name: Cache ImageMagick
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-name: cache-ImageMagick
         with:
@@ -141,7 +141,7 @@ jobs:
           sudo apt-get install -y texlive-fonts-recommended || true
 
       - name: Cache ImageMagick
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         env:
           cache-name: cache-ImageMagick
         with: