Pollution from .mlc_config.json

1) .mlc_config is getting added to the root of every repo - a file that is used to configure the github
https://github.com/search?q=org%3Aai-cfia%20.mlc_config&type=code

https://github.com/ai-cfia/github-workflows/blob/8521ad203de073af433485a150dc00597ca0380b/.github/workflows/workflow-markdown-check.yml#L24

2) this was created to fix links to LinkedIn where it is returning a non-standard 999 HTTP code for links accessed without a proper account

https://excellentwebcheck.com/blogs/what-is-http-999-request-denied-response-code

3) this really should be a parameter to the github-workflows with default only expecting 200 (we generally shouldn't be pointing to pages that are 403

* [x] modify workflow-markdown-check.yml to take list of acceptable status code and reasonable default
* [ ] remove .mlc_config from repo where it was inserted
* [x] fix the documentation to not require that file anymore