Separate dependencies and browser installation (#956)

- deps as root
- browser as discourse user

Author: jjaffeux

image/discourse_test/Dockerfile

@@ -38,6 +38,9 @@ RUN cd /var/www/discourse && sudo -E -u discourse -H bundle exec rake plugin:ins
     sudo -E -u discourse -H bundle exec ruby script/install_minio_binaries.rb
 
 RUN cd /var/www/discourse && \
-    pnpm playwright install --with-deps --no-shell chromium
+    pnpm playwright install ffmpeg
+
+RUN cd /var/www/discourse && \
+    sudo -E -u discourse -H pnpm playwright install --no-shell chromium
 
 ENTRYPOINT ["sudo", "-E", "-u", "discourse", "-H", "ruby", "script/docker_test.rb"]