release notes: mention increased min android version

ref #10485

Author: SomberNight

RELEASE-NOTES

@@ -21,6 +21,7 @@
  * QML GUI & Android:
     - new: support renaming wallets (#10573)
     - changed: update python-for-android, Qt and NDK versions (#10485)
+      - this bumps the minimum OS requirement: Android 6.0->8.0
     - changed: improve wallet history scrolling performance (#10615)
     - changed: give feedback about ongoing lightning channel reestablishment in invoice view (#10698)
     - fix: race condition causing UI to show incorrect payment status (#10631)

contrib/android/Readme.md

@@ -10,7 +10,7 @@ To generate an APK file, follow these instructions.
 ✓ _These binaries should be reproducible, meaning you should be able to generate
    binaries that match the official releases._
 
-- _Minimum supported target system (i.e. what end-users need): Android 6.0 (API 23)_
+- _Minimum supported target system (i.e. what end-users need): Android 8.0 (API 26)_
 
 This assumes an Ubuntu (x86_64) host, but it should not be too hard to adapt to another
 similar system.