replace graphicsmagick with libmagick++-dev in test workflow

fixes tests for 24.04 and reflects the install guide

Author: stuzart

.github/workflows/tests.yml

@@ -61,7 +61,7 @@ jobs:
           sudo apt install -y software-properties-common
           sudo add-apt-repository ppa:deadsnakes/ppa
           sudo apt update
-          sudo apt install -y graphicsmagick graphviz libcurl4-gnutls-dev libreoffice poppler-utils build-essential \
+          sudo apt install -y libmagick++-dev graphviz libcurl4-gnutls-dev libreoffice poppler-utils build-essential \
             git imagemagick libgmp-dev python3.9-dev python3.9-distutils python3-pip
       - name: Checkout code
         uses: actions/checkout@v4