Fix stripeAnimation variable spelling

Editor assessment

The subject states the fix precisely: the stripeAnimation variable spelling was corrected in the progress package. The progress scope is a proper component noun, the refactor type fits an internal renaming with no behavior change, and both the variable and the defect class are named, so the reader knows exactly what happened. There is no body, acceptable for a one-identifier correction whose headline is complete. No footers appear. The lowercase imperative phrasing is clean. Compact and self-sufficient. Labeling it refactor correctly promises no behavior change, which matters for readers bisecting history.