Update documentation of compression in HTTP request

[basgroot]

What?

Update documentation of compression in HTTP request The params.md has no description of the default compression.

Checklist

• [x] I have used a meaningful title for the PR.

• [x] I have described the changes I've made in the "What?" section above.

• [x] I have performed a self-review of my changes.

• [ ] I have run the npm start command locally and verified that the changes look good.

• [x] I have made my changes in the docs/sources/next folder of the documentation.

• [x] I have reflected my changes in the docs/sources/v{most_recent_release} folder of the documentation.

• [ ] I have reflected my changes in the relevant folders of the two previous k6 versions of the documentation (if still applicable to previous versions).

  Related PR(s)/Issue(s)

  I ended up here from the Suggest Edits link, so no Issue has been created.

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