sleeplog: tweak changelog

Author: thyttan

apps/sleeplog/ChangeLog

@@ -21,5 +21,5 @@
 0.23: Fix important bug with HRM data being undefined when compared - broken apps should work properly now
 0.24: Change day title to be easier to read, capitalization, and improved documentation/tuning guide in README.
 0.25: Put HRM mode behind the setting `Prefer HRM` which defaults to `false`.
-      Please turn it on if you want the recent HRM behavior. The new default
+      Please enable if you want the HRM behavior from v0.21. The new default
       will be more in line with how version 0.20 worked.