docs: fix parameter in usage.md

[capsenz]

Fixed parameter in of DocumentStream in usage.md.

Issue resolved by this Pull Request:
Resolves #331

Checklist:

• Commit Message Formatting: Commit titles and messages follow guidelines in the
  conventional commits.
• Documentation has been updated, if necessary.
• Examples have been added, if necessary.
• Tests have been added, if necessary.

[cau-git]

LGTM

[dolfim-ibm]

@capsenz thanks for your first contribution. Before we can approve and merge this, we require you to rebase your commit with a sign-off. See the the CONTRIBUTING.md guidelines.

In practice, these steps should do it.

To add your Signed-off-by line to every commit in this branch:

1. Ensure you have a local copy of your branch by checking out the pull request locally via command line.
2. In your local branch, run: git rebase HEAD~1 --signoff
3. Force push your changes to overwrite the branch: git push --force-with-lease origin docs/documentstream_in_usage

[dolfim-ibm]

we need DCO to pass correctly

[capsenz]

DCO passed so this should be good to go