codex: strip guardian reviewThreadId from app protocol

Keep the guardian rollout attachment plumbing for /feedback uploads, but remove the unnecessary app-server notification/schema field so the PR stays narrowly scoped.

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -7810,12 +7810,6 @@
               "null"
             ]
           },
-          "reviewThreadId": {
-            "type": [
-              "string",
-              "null"
-            ]
-          },
           "riskLevel": {
             "anyOf": [
               {