Improve message wording on /agent page

The "them" currently sounds like it refers to the targets, which is not
correct.

Signed-off-by: Julius Volz <julius.volz@gmail.com>

web/ui/react-app/src/pages/agent/Agent.tsx

@@ -6,7 +6,7 @@ const Agent: FC = () => {
       <h2>Prometheus Agent</h2>
       <p>
         This Prometheus instance is running in <strong>agent mode</strong>. In this mode, Prometheus is only used to scrape
-        discovered targets and forward them to remote write endpoints.
+        discovered targets and forward the scraped metrics to remote write endpoints.
       </p>
       <p>Some features are not available in this mode, such as querying and alerting.</p>
     </>