Fix minor typo in documentation.

[pouwerkerk]

JENKINS-68424

Fixes a small typo in documentation, by changing "expoand" to "expand".

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. This is simply a reminder of what we are going to look for before merging your code. If a checkbox or line does not apply to this pull request, delete it. We prefer all checkboxes to be checked before a pull request is merged

• I have read the CONTRIBUTING doc
• I have referenced the Jira issue related to my changes in one or more commit messages
• I have added documentation as necessary
• No Javadoc warnings were introduced with my changes
• No spotbugs warnings were introduced with my changes
• Documentation in README has been updated as necessary
• I have interactively tested my changes

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Further comments

This is a really minor typo fix. Just noticed it when reading the docs and hope this is helpful and not annoying!