Markdown: format correctly table when columns are missing

[yanapeycheva]

Description

Resolves #15970.

Checklist

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in the docs/ directory).
• (If the change is user-facing) I’ve added my changes to changelog_unreleased/*/XXXX.md file following changelog_unreleased/TEMPLATE.md.
• I’ve read the contributing guidelines.

✨Try the playground for this PR✨

[kachkaev]

@fisker WDYT? Seems like this PR can resolve the issue you’ve opened: #15970

[fisker]

The output looks good.

The CI seems not running.

[yanapeycheva]

Hello. I forgot to run yarn fix before the pull request. Is it possible that this causes the pipeline to fail? I just pushed the commit with the formatted file.

[kachkaev]

@yanapeycheva CI is still failing. Can you have another look please? We’re close 🤞

[kachkaev]

Looks like you need to update a couple of test snapshots. Try yarn test -u locally to update them. You can find a few more details in CONTRIBUTING.md.