lower logging level for stopping actors (#859)

Summary:
Pull Request resolved: #859

error! will show up on user screen. It is not a critical error per se
as it doesn't throw an error or requires some action item to mitigate it. Lower
it to warn!

 {F1981181213}

Reviewed By: LucasLLC

Differential Revision: D80192060

fbshipit-source-id: 7a6108102250ae1806f231a1c81403292d1e2177

Author: James Sun

hyperactor_mesh/src/proc_mesh.rs

@@ -502,16 +502,16 @@ impl ProcMesh {
         for (actor_id, result) in results {
             match result {
                 Ok(StopActorResult::Timeout) => {
-                    tracing::error!("timed out while stopping actor {}", actor_id);
+                    tracing::warn!("timed out while stopping actor {}", actor_id);
                 }
                 Ok(StopActorResult::NotFound) => {
-                    tracing::error!("no actor {} on proc {}", actor_id, actor_id.proc_id());
+                    tracing::warn!("no actor {} on proc {}", actor_id, actor_id.proc_id());
                 }
                 Ok(StopActorResult::Success) => {
                     tracing::info!("stopped actor {}", actor_id);
                 }
                 Err(e) => {
-                    tracing::error!("error stopping actor {}: {}", actor_id, e);
+                    tracing::warn!("error stopping actor {}: {}", actor_id, e);
                 }
             }
         }