chore: increase the timeout for stable diffusion example (mosecorg#427)

Signed-off-by: Keming <kemingy94@gmail.com>

README.md

@@ -149,7 +149,7 @@ python examples/stable_diffusion/server.py --help
 Then let's start the server with debug logs:
 
 ```shell
-python examples/stable_diffusion/server.py --log-level debug
+python examples/stable_diffusion/server.py --log-level debug --timeout 30000
 ```
 
 And in another terminal, test it:

docs/source/examples/stable_diffusion.md

@@ -15,6 +15,10 @@ docker run --rm --gpus all -p 8000:8000 sd:serving
 :code: python
 ```
 
+```shell
+python server.py --timeout 30000
+```
+
 ## Client
 
 ```shell

src/tasks.rs

@@ -121,7 +121,8 @@ impl TaskManager {
     pub(crate) async fn submit_task(&self, data: Bytes) -> Result<Task, ServiceError> {
         let (id, rx) = self.add_new_task(data)?;
         if let Err(err) = time::timeout(self.timeout, rx).await {
-            warn!(%id, %err, "task was not completed in the expected time");
+            warn!(%id, %err, "task was not completed in the expected time, if this happens a lot, \
+                you might want to increase the service timeout");
             self.delete_task(id, false);
             return Err(ServiceError::Timeout);
         }