Update release notes

Author: salimbraksa

RELEASE-NOTES.txt

@@ -14,6 +14,7 @@
 * [*] [internal] Editor: Only register core blocks when `onlyCoreBlocks` capability is enabled [https://github.com/wordpress-mobile/gutenberg-mobile/pull/5293]
 * [**] [internal] Disable StockPhoto and Tenor media sources when Jetpack features are removed [#19826]
 * [*] [Jetpack-only] Fixed a bug where analytics calls weren't synced to the user account. [#19926]
+* [*] [Jetpack-only] Fixed a bug where the Login flow was restarting every time the app enters the foreground. [#19961]
 
 21.4
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