Update ChangeLog.d/alert_reentrant.txt

Co-authored-by: Gilles Peskine <gilles.peskine@arm.com>
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/alert_reentrant.txt b/ChangeLog.d/alert_reentrant.txt
index 2d1dc60..691d64c 100644
--- a/ChangeLog.d/alert_reentrant.txt
+++ b/ChangeLog.d/alert_reentrant.txt
@@ -2,4 +2,4 @@
    * Fix bug in the alert sending function mbedtls_ssl_send_alert_message()
      potentially leading to corrupted alert messages being sent in case
      the function needs to be re-called after initially returning
-     MBEDTLS_SSL_WANT_WRITE.
+     MBEDTLS_SSL_WANT_WRITE. Fixes #1916.