doc: link to issue for the use of forked repo of aspectj

Author: Pankaj Agrawal

example/HelloWorldFunction/pom.xml

@@ -80,6 +80,7 @@
     <build>
       <plugins>
         <plugin>
+            <!-- Refer https://github.com/awslabs/aws-lambda-powertools-java/issues/50 -->
              <groupId>com.nickwongdev</groupId>
              <artifactId>aspectj-maven-plugin</artifactId>
              <version>1.12.6</version>