[21486] Fix HelloWorld example with TopicDataType refactored code

[JesusPoderoso]

Description

When updating the Fast DDS python code to the new TopicDataType methods, the HelloWorld example update was missed. This PR updates changes those calls to use the new API.

Fixes #182

Contributor Checklist

• Commit messages follow the project guidelines.
• ❌: Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
  • We will update the CI so it runs the example in a follow-up
• ❌: Changes are API compatible.
• N/A Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.