Install covered gem for sus config

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: samuel-williams-shopify

.github/workflows/test-ruby-gc-bug.yaml

@@ -98,7 +98,7 @@ jobs:
         for variant in fixed buggy caseC; do
           echo "=== Building io-event for ruby-${variant} ==="
           export PATH=$HOME/.rubies/ruby-${variant}/bin:$PATH
-          gem install sus --no-document -q
+          gem install sus covered --no-document -q
 
           mkdir -p /tmp/ext-${variant}
           cp -r ext/* /tmp/ext-${variant}/