Add more context to note (#20081)

* Add more context to note

* Apply suggestions from code review

Co-authored-by: Janine Chan <64388808+janine-c@users.noreply.github.com>

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Co-authored-by: Janine Chan <64388808+janine-c@users.noreply.github.com>

Author: estherk15

http_check/README.md

@@ -79,7 +79,7 @@ See [service_checks.json][10] for a list of service checks provided by this inte
 
 To disable `http.ssl_cert`, set `check_certificate_expiration` to false.
 
-**Note:** To set an alert on these service checks, create a [Network Monitor][11].
+**Note:** To monitor HTTP error codes (such as 404) or view the first 400 characters of an HTTP response, create a [Network Monitor][11] based on these service checks.
 
 ## Troubleshooting