Remove Supermaven-related code from Zed (#50537)

Follow-up of https://github.com/zed-industries/zed/pull/49317

See also https://supermaven.com/blog/sunsetting-supermaven

- N/A

docs/src/reference/all-settings.md

@@ -1800,17 +1800,7 @@ While other options may be changed at a runtime and should be placed under `sett
 }
 ```
 
-3. Use Supermaven as the edit prediction provider:
-
-```json [settings]
-{
-  "edit_predictions": {
-    "provider": "supermaven"
-  }
-}
-```
-
-4. Turn off edit predictions across all providers
+3. Turn off edit predictions across all providers
 
 ```json [settings]
 {