Correct description about thickness prop

Editor assessment

The subject states the correction precisely: the description of the thickness prop in the progress docs was corrected. The progress scope is a proper component noun, the docs type matches, and the target prop is named, so the reader knows exactly what was fixed even without the before-and-after text. There is no body, acceptable for a small documentation correction whose headline identifies the prop and the defect class. No footers appear. The lowercase imperative phrasing is clean. Clear, targeted, and self-sufficient.