Document #53 broken import on recent systems in release notes

Signed-off-by: Aron Heinecke <aron.heinecke@t-online.de>

Author: 0xpr03

fastlane/metadata/android/en-US/changelogs/21.txt

@@ -1,4 +1,5 @@
  - Fix ui feedback when missing times-to-solve
  - Fix broken list creation button on old systems
  - Fix broken UI when switching to quick-training mode
- - A bunch of chores regarding updates and deprecations
+ - A bunch of chores regarding updates and deprecations
+ - Known Bug: Import/Export missing files in selection on latest android