Add uppercase in progressbar specs

[lcordobapuerto]

Checklist
(Check off all the items before submitting)

• Build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

Purpose
Add the uppercase token in the progressbar specifications.
Description
The Progressbar component was outdated in our documentation, so the purpose of this PR is to update the specifications of the Progressbar by adding the uppercase token of its label element.