fix link, run link check in quiet mode (#5257)

com.unity.ml-agents/CHANGELOG.md

 #### ml-agents / ml-agents-envs / gym-unity (Python)
 - The `--resume` flag now supports resuming experiments with additional reward providers or
  loading partial models if the network architecture has changed. See
- [here](https://github.com/Unity-Technologies/ml-agents/blob/release-16_docs/docs/Training-ML-Agents.md#loading-an-existing-model)
+ [here](https://github.com/Unity-Technologies/ml-agents/blob/release_16_docs/docs/Training-ML-Agents.md#loading-an-existing-model)
  for more details. (#5213)
 
 ### Bug Fixes

utils/run_markdown_link_check.py

     )
 
     for f in args.files:
-        subprocess_args = ["markdown-link-check", "-c", config_file, f]
+        subprocess_args = ["markdown-link-check", "-q", "-c", config_file, f]
         subprocess.check_call(subprocess_args)