(CI) missing sudo

Src-commit: 56170929e8a230475c138ca6aacd675ac206d7ae

Author: jfmc

.github/workflows/build.yml

@@ -59,7 +59,7 @@ jobs:
       # Additional setup for devenv (specially documentation generation)
       - run: |
           sudo apt-get install emacs-nox texlive-latex-base texlive-binaries
-          sed -i '/disable ghostscript format types/,+6d' /etc/ImageMagick-6/policy.xml
+          sudo sed -i '/disable ghostscript format types/,+6d' /etc/ImageMagick-6/policy.xml
         if: (matrix.sys.os == 'ubuntu-latest' && matrix.sys.inskind == 'devenv')
       # Checks-out repo under $GITHUB_WORKSPACE
       - uses: actions/checkout@v2