ci: try installing xvfb before refreshing the package index

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.github/workflows/gradle.yml

@@ -46,8 +46,10 @@ jobs:
         key: gradle-dist-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties', 'gradle/wrapper/GradleWrapperNeo.java') }}
     - name: Install Xvfb
       run: |
-        # Skip the slow apt update when the runner image already has it.
-        command -v xvfb-run >/dev/null || { sudo apt-get update && sudo apt-get install -y xvfb; }
+        # Installing is the slowest setup step, so skip it when the runner already has xvfb, and
+        # only refresh the package index when a plain install fails.
+        command -v xvfb-run >/dev/null || sudo apt-get install -y --no-install-recommends xvfb \
+          || { sudo apt-get update && sudo apt-get install -y --no-install-recommends xvfb; }
     # One Gradle run builds, tests and runs the code and translation checks, so the
     # project is configured and compiled once instead of in two workflows.
     - name: Build and check with Gradle