CHANGELOG: reword to better clarify fixes

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

Author: msfjarvis

CHANGELOG.md

@@ -6,7 +6,7 @@ All notable changes to this project will be documented in this file.
 
 ### Fixed
 
--   Remember passphrase option did not work with keys that had empty passphrases and were generated before 2019
+-   Remember passphrase option did not work with old-style keys (generated either before 2019 or by passing `-m PEM` to new versions of OpenSSH)
 
 ### Added