chore(metrics): Clean up metrics CLI docs (#14654)

Metrics have been deprecated since October 7th 2024, so this is no
longer valid, and we should remove instructions on how to send metrics,
because this doesn't even work.

This PR getsentry/sentry-cli#2710 will clean up
metrics commands in CLI, but this can be cleaned up separately.

Author: vgrozdanic

docs/cli/metrics.mdx

@@ -1680,6 +1680,10 @@ const USER_DOCS_REDIRECTS: Redirect[] = [
     from: '/learn/cli/releases/',
     to: '/cli/releases/',
   },
+  {
+    from: '/cli/metrics/',
+    to: '/cli/send-event/',
+  },
   {
     from: '/workflow/alerts-notifications/',
     to: '/product/alerts/',