fix: install missing fonts (avoid warnings)

Author: wpbonelli

.github/workflows/ex-rtd.yml

@@ -41,6 +41,9 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt install texlive-latex-extra texlive-science fonts-liberation
+          echo ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula select true | sudo debconf-set-selections
+          sudo apt-get install ttf-mscorefonts-installer
+          sudo rm -rf ~/.cache/matplotlib
 
       - name: Install pandoc
         run: |