@BenjaminW. is right (in the comments). Thanks.

First, I just changed runs on: ubuntu-latest to runs on: ubuntu-22.04.

Then I tried this:

 runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - name: Install libmagickwand-dev
        run: sudo apt-get install libmagickwand-dev

Both work, and I'm not sure which solution is better.