LOG4J2-2972 Fix AsyncAppender builder annotation.
diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/AsyncAppender.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/AsyncAppender.java
index 141eb95..8c4ca83 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/AsyncAppender.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/AsyncAppender.java
@@ -33,6 +33,7 @@
 import org.apache.logging.log4j.core.config.Configuration;
 import org.apache.logging.log4j.core.config.ConfigurationException;
 import org.apache.logging.log4j.core.config.Property;
+import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
 import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
 import org.apache.logging.log4j.core.filter.AbstractFilterable;
 import org.apache.logging.log4j.core.impl.Log4jLogEvent;
@@ -231,7 +232,7 @@
         }
     }
 
-    @PluginFactory
+    @PluginBuilderFactory
     public static Builder newBuilder() {
         return new Builder();
     }