updated RELEASE-NOTES.txt

Author: sla8c

RELEASE-NOTES.txt

@@ -7,6 +7,7 @@
 * [**] People: you can now manage Email Followers on the People section! [#17854]
 * [*] Stats: fix navigation between Stats tab. [#17856]
 * [*] Quick Start: Fixed a bug where a user logging in via a self-hosted site not connected to Jetpack would see Quick Start when selecting "No thanks" on the Quick Start prompt. [#17855] 
+* [*] Stats: can now add insights card from navigation bar [#17867]
 
 19.1
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