Tests: Pass WPT certificate to WebDriver when running CI tests

Author: https://github.com/ADKaster
Commit: https://github.com/SerenityOS/serenity/commit/2819067370
Pull-request: https://github.com/SerenityOS/serenity/pull/23186

Tests/LibWeb/WPT/run.sh

@@ -68,6 +68,8 @@ python3 ./wpt/wpt run ladybird \
                   --include-manifest include.ini \
                   --metadata ./metadata \
                   --manifest ./MANIFEST.json \
+                  --webdriver-arg="--certificate=${PWD}/wpt/tools/certs/cacert.pem" \
+                  --webdriver-arg="--certificate=${SERENITY_SOURCE_DIR}/Build/lagom/cacert.pem" \
                   --log-raw "${wpt_run_log_filename}"
 
 # Update expectations metadata files if requested