codex: revert thread command output delta raw-bytes followup (#14988)

codex-rs/app-server-protocol/schema/json/ServerNotification.json

@@ -725,17 +725,8 @@
     "CommandExecutionOutputDeltaNotification": {
       "properties": {
         "delta": {
-          "description": "Best-effort UTF-8 view of the output chunk for backwards compatibility.",
           "type": "string"
         },
-        "deltaBase64": {
-          "default": null,
-          "description": "Exact raw bytes for the chunk, base64-encoded.",
-          "type": [
-            "string",
-            "null"
-          ]
-        },
         "itemId": {
           "type": "string"
         },