Merge several code monitoring sub pages (#1287)

I found it a bit chaotic to move between several pages for a feature as
simple as code monitoring, so I reduced some redundant content and
consolidated it to a length where I feel ok about having it be a single
page only. I think there's more potential for simplification here, but
this feels like a good improvement regardless.

Test plan: Review.

Author: eseliger

docs/cloud/index.mdx

@@ -34,9 +34,10 @@ As part of this service you will receive a number of benefits from our team, inc
 All of Sourcegraph's features are available on Sourcegraph Cloud instances out-of-the-box, including but not limited to:
 
 - [Cody](/cody)
+- [Deep Search](/deep-search)
 - [Server-side Batch Changes](/batch-changes/server-side)
 - [Precise code navigation powered by auto-indexing](/code-search/code-navigation/auto_indexing)
-- [Code Monitoring](/code_monitoring/) (including [email delivery](#managed-smtp) of notifications)
+- [Code Monitoring](/code_monitoring/)
 - [Code Insights](/code_insights/)
 
 ### Access restrictions