doc: coder-server module does not have offline attribute (#180)

code-server/README.md

@@ -79,16 +79,3 @@ module "code-server" {
   extensions = ["dracula-theme.theme-dracula", "ms-azuretools.vscode-docker"]
 }
 ```
-
-### Offline Mode
-
-Just run code-server in the background, don't fetch it from GitHub:
-
-```tf
-module "code-server" {
-  source   = "registry.coder.com/modules/code-server/coder"
-  version  = "1.0.8"
-  agent_id = coder_agent.example.id
-  offline  = true
-}
-```