Update the endpoint picker proposal

Author: ahg-g

docs/proposals/003-endpoint-picker-protocol/README.md

@@ -12,7 +12,7 @@ The EPP MUST implement the Envoy
 [external processing service](https://www.envoyproxy.io/docs/envoy/latest/api-v3/service/ext_proc/v3/external_processor)protocol.
 
 For each HTTP request, the EPP MUST communicate to the proxy the picked model server endpoint, via
-adding the `target-pod` HTTP header in the request, or otherwise return an error.
+adding the `x-gateway-destination-endpoint` HTTP header in the request and as an unstructured entry in the [dynamic_metadata](https://github.com/envoyproxy/go-control-plane/blob/c19bf63a811c90bf9e02f8e0dc1dcef94931ebb4/envoy/service/ext_proc/v3/external_processor.pb.go#L320) field of the ext-proc response, or otherwise return an error.
 
 ## Model Server Protocol
 
@@ -62,4 +62,4 @@ The model server MUST expose the following LoRA adapter metrics via the same Pro
   Requests will be queued if the model server has reached MaxActiveAdapter and canno load the
   requested adapter. Example: `"max_lora": "8"`.
   * `running_lora_adapters`: A comma separated list of adapters that are currently loaded in GPU
-    memory and ready to serve requests. Example: `"running_lora_adapters": "adapter1, adapter2"`
+    memory and ready to serve requests. Example: `"running_lora_adapters": "adapter1, adapter2"`