ci: upgrade GH workflows and fix markdown linting

[derberg]

fixes: #940

additionally:

• removed mlc_config.json that was no longer needed as we removed links validation for now
• linter workflow did not work for soooooo longggggg -> https://github.com/asyncapi/spec/actions/runs/5738753612/job/15552977211. So I introduced another too, and did some basic fixes in markdown (headers and white spaces)

[derberg]

ok, new linter workflow works, and fails if error simulated (I made changes in config) https://github.com/asyncapi/spec/actions/runs/5739972585/job/15556776030?pr=958

[derberg]

@jonaslagoni how is this affecting 3.0 work? I guess the problem might be with the asyncapi.md document only, right?

[jonaslagoni]

@derberg the problems it highlight, is not really problems when rendered in the website is it? 🤨

[derberg]

@jonaslagoni you mean headings and whitespaces?

• whitespaces dunno, but it was easy as autofixed with --fix flag
• headings -> is was actually strange the h difference that causes such strange indent in TOC
  

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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[jonaslagoni]

@derberg once this is merged I would assume we can discard any of the asyncapi.md changes and just run the same markdown lint again and commit that, right?

[jonaslagoni]

So a manual merge commit is needed for sure yea

[smoya]

Can we proceed merging this? cc @derberg @jonaslagoni Is anything else missing?

[jonaslagoni]

@smoya yep, just need your review 😄

[smoya]

LGTM! 🚀🌔

[smoya]

/rtm

[asyncapi-bot]

🎉 This PR is included in version 3.0.0-next-major-spec.18 🎉

The release is available on GitHub release

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[asyncapi-bot]

🎉 This PR is included in version 3.0.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀