The change of 
to 
is a very common inaccuracy in Chopin's editions by M. Schlesinger – see note to Etude in C, Op. 10 No. 1. At this point, the alleged change of marking would only be a reminder of the time signature in force from the beginning of the piece. The error was corrected – perhaps at Chopin's request – in FE2 (→EE).
Compare the passage in the sources »
category imprint: Differences between sources
issues: Errors in FE, Authentic corrections of FE
notation: Rhythm