Merge pull request #25 from PHPCSStandards/feature/ghactions-fix-xmllint

GH Actions/CS: fix build failure

Author: jrfnl

.github/workflows/ci.yml

@@ -35,7 +35,9 @@ jobs:
         run: composer install --prefer-dist --no-interaction --no-progress
 
       - name: Setup xmllint
-        run: sudo apt-get install --no-install-recommends -y libxml2-utils
+        run: |
+          sudo apt-get update
+          sudo apt-get install --no-install-recommends -y libxml2-utils
 
       # Show violations inline in the file diff.
       # @link https://github.com/marketplace/actions/xmllint-problem-matcher