Update ChangeLog

Author: RKBoss6

apps/sleeplog/ChangeLog

@@ -17,3 +17,4 @@
 0.19: Write sleep state into health event's .activity field
 0.20: Increase default sleep thresholds, tweak settings to allow higher ones to be chosen
 0.21: Use HRM data is polling is enabled, and add appropriate thresholds in settings. Change settings to feel more intuitive, rather than copied settings in different pages.
+0.22: Fix bug with HRM threshold not updating