Save AtomicBoolean allocation in Arc

There is no reason to use an atomic boolean in this case,
as there aren't any compareAndSwap (or similar) operations,
just plain reading and writing of the field, which means
a volatile boolean is perfectly fine

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/RequestContext.java

@@ -12,7 +12,6 @@
 import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import javax.enterprise.context.BeforeDestroyed;
@@ -168,7 +167,7 @@ public void destroy(ContextState state) {
         }
         if (state instanceof RequestContextState) {
             RequestContextState reqState = ((RequestContextState) state);
-            reqState.isValid.set(false);
+            reqState.isValid = false;
             synchronized (state) {
                 Map<Contextual<?>, ContextInstanceHandle<?>> map = ((RequestContextState) state).map;
                 // Fire an event with qualifier @BeforeDestroyed(RequestScoped.class) if there are any observers for it
@@ -228,11 +227,12 @@ private static Notifier<Object> createDestroyedNotifier() {
     static class RequestContextState implements ContextState {
 
         private final Map<Contextual<?>, ContextInstanceHandle<?>> map;
-        private final AtomicBoolean isValid;
+
+        private volatile boolean isValid;
 
         RequestContextState(ConcurrentMap<Contextual<?>, ContextInstanceHandle<?>> value) {
             this.map = Objects.requireNonNull(value);
-            this.isValid = new AtomicBoolean(true);
+            this.isValid = true;
         }
 
         @Override
@@ -243,7 +243,7 @@ public Map<InjectableBean<?>, Object> getContextualInstances() {
 
         @Override
         public boolean isValid() {
-            return isValid.get();
+            return isValid;
         }
 
     }