docs: remove architecture diagram (#3615)

The diagram was more confusion than helpful.

docs/about/architecture.md

@@ -1,9 +1,5 @@
 # Architecture
 
-<p align="center">
-  <img src="./images/architecture.png" width="700px">
-</p>
-
 ## Agents
 
 An agent is the Coder service that runs within a user's remote workspace.

docs/manifest.json

@@ -15,7 +15,7 @@
           "title": "Architecture",
           "description": "Learn how Coder works",
           "icon_path": "./images/icons/protractor.svg",
-          "path": "./architecture.md"
+          "path": "./about/architecture.md"
         }
       ]
     },