ci: include required WebKit GStreamer pipeline plugins

Co-Authored-By: OpenAI Codex <codex@openai.com>

Author: nicohrubec

.github/workflows/benchmark-browser-system-deps.yml

@@ -97,6 +97,8 @@ jobs:
       - name: Install candidate headless WebKit runtime packages
         run: |
           webkit_packages=(
+            gstreamer1.0-plugins-base
+            gstreamer1.0-plugins-good
             libavif16
             libevent-2.1-7t64
             libflite1