Fix inconsistency in javadoc for WorkflowInterface (#2232)

[mackler]

What was changed

This modifies slightly the code example in the javadoc for the @WorkflowInterface annotation.

Why?

The example code had a slight inconsistency with the accompanying text describing it.

Checklist

1. Closes #2232

2. How was this tested:

Inspected the documentation visually. Neither compiled nor run.