add legal directory ignore to GH Action for vale

Author: TC-MO

.github/workflows/vale.yaml

@@ -22,6 +22,7 @@ jobs:
                         apify-api/openapi/README.md
                         apify-api/openapi/paths/README.md
                         apify-api/openapi/components/README.md
+                        sources/legal/*/**.{md,mdx}
                     separator: ','
 
             -   uses: errata-ai/vale-action@reviewdog