chore: remove non-existent db2 integration from coverage comment workflow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: julian-risch

.github/workflows/CI_coverage_comment.yml

@@ -16,7 +16,6 @@ on:
       - "Test / chroma"
       - "Test / cohere"
       - "Test / cometapi"
-      - "Test / db2"
       - "Test / deepeval"
       - "Test / docling_serve"
       - "Test / dspy"