[23.0] Fix invalid link to "workflows by owner"

[ElectronicBlueberry]

Fixes #15974 by using the owner computed, instead of item.username which does not exist on workflows

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. Publish a workflow
  2. Navigate to published workflow
  3. Click 'Published Workflows by Username'
  4. Check URL

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[martenson]

thanks!