Revert "Edit env var to take manual input on render"

This reverts commit bffa432b29.

render.yaml

@@ -46,6 +46,9 @@ services:
     healthCheckPath: /health
     envVars:
       - key: ORIGIN_WHITELIST
-        sync: false
+        fromService:
+          type: web
+          name: "Owlbear Rodeo Legacy"
+          envVarKey: RENDER_EXTERNAL_HOSTNAME
       - key: PORT
         value: 9000