Disable Markdown link check

[bedrich-schindler]

Markdown link check is failing due to following problems:

1. It is marked as deprecated, see https://github.com/gaurav-nelson/github-action-markdown-link-check
2. It has started to fail with HTTP 403 error due to StackOverflow's Cloudfare firewall:

ERROR: 1 dead links found!
[✖] https://stackoverflow.com/q/40722882 → Status: 403

Due to inability to merge pull request, after discussion with @mbohal, I disable this plugin immediately.

We can discuss whether we want to find replacement or not.

[adamkudrna]

Related PR in Spirit: lmc-eu/spirit-design-system#2077

[mbohal]

We will try:

1. update plugin
2. look for option for specifying known broken links
3. consider handling broken link as warnings