fix: use concurrent hashmap (#1017)

Signed-off-by: Manuel Serra <ma.serra@teamsystem.com>
Co-authored-by: Artur Souza <artursouza.ms@outlook.com>

Author: manuelserradev

sdk-actors/src/main/java/io/dapr/actors/runtime/ActorStateManager.java

@@ -18,10 +18,10 @@
 import reactor.core.publisher.Mono;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * Manages state changes of a given Actor instance.
@@ -60,7 +60,7 @@ public class ActorStateManager {
     this.stateProvider = stateProvider;
     this.actorTypeName = actorTypeName;
     this.actorId = actorId;
-    this.stateChangeTracker = new HashMap<>();
+    this.stateChangeTracker = new ConcurrentHashMap<>();
   }
 
   /**