[build] run apt-get update on github ubuntu workflow

Change-Id: I66de8d398c662a0b0933760c6a753ea8f8b63b7d

Author: stbuehler

.github/workflows/ci-linux.yml

@@ -19,6 +19,7 @@ jobs:
             ruby-kramdown
             libxml2-utils
           )
+          sudo apt-get update
           sudo apt-get install "${pkgs[@]}"
       - name: Build docs
         run: |
@@ -58,6 +59,7 @@ jobs:
             python3
             python3-pycurl
           )
+          sudo apt-get update
           sudo apt-get install "${pkgs[@]}"
       - name: meson setup
         run: meson setup mesonbuilddir