update unhealthy sessions

Author: michellewzhang

includes/insights-session-health-body.mdx

@@ -20,9 +20,9 @@ The chart view will be saved into local storage, so when you come back to the pa
 
 For the Frontend module, the following charts are available:
 
-- [Error Free Sessions](/product/releases/health/#errored)
-- [Session Health](/product/releases/health/#session-status)
-- [Session Counts](/product/releases/health/#session-status)
+- Unhealthy Sessions
+- Session Health
+- Session Counts
 - User Health
 - User Counts
 - [Issues](/product/issues/)
@@ -31,6 +31,8 @@ Most of these charts, with the exception of the Issues chart, are based on sessi
 
 The Session Health, Session Counts, User Health, and User Counts charts aim to break down trends in how your sessions are performing status-wise. The status options are healthy, crashed, errored, or abnormal. [Learn more about session statuses](/product/releases/health/#session-status).
 
+The Unhealthy Sessions chart combines the total rate of errored, crashed, and abnormal sessions into one line.
+
 The Issues chart is the only chart that does not rely on session-backed data. Instead, it shows the number of new and resolved issues for that project over time. It also gives a preview of the two most recently seen issues for that project. The chart header, when hovered, contains a link to view all issues for that project.
 
 ![Issues chart](./common-imgs/img/frontend-insights-issue-chart.png)