update lerna/markdown-lint

[gatzjames]

Highlights:

• Lerna 4 -> 5 breaking changes shouldn't affect our pipeline
• Ran markdown-lint and fixed a warning

TODO:

• [ ] Figure out why running npm run bootstrap updates all package-lock.json files with tabs
• [ ] Update the release start workflow and validate everything works as expected

[DMarby]

The new version of lerna should be supporting v2 package-lock.json files correctly, so with this upgrade we should also remove the following step in release start workflow: https://github.com/Kong/insomnia/blob/develop/.github/workflows/release-start.yml#L74-L75

Would be good to test it before merging however.

[filfreire]

Heads up @gatzjames @DMarby - I was having a quick look into this one locally and there are a few issues that require attention before we merge. I suspect same applies to #5081.

• ⚠️ Running bootstrap indents the lock files from spaces to tabs, but in some cases also from tabs to spaces 😕 🤷

• ✅ We seem to no longer indeed need the line that @DMarby mentioned on release-start, that bit seems to now be fixed, examples:

[jackkav]

cleaning up stale PRs