Update apt before installing packages

.github/workflows/test.yml

@@ -36,6 +36,8 @@ jobs:
     - uses: actions/checkout@v2
     - name: Setup ImageMagick policy
       run: sudo sh -c 'echo '\''<policymap><policy domain="coder" rights="read|write" pattern="PDF" /></policymap>'\'' > /etc/ImageMagick-6/policy.xml'
+    - name: Update package list
+      run: sudo apt update
     - name: Install ghostscript to process PDF
       run: sudo apt-get -y install ghostscript
     - name: Install libvips-dev for Carrierwave::Vips