Update deploymentGroupAppspec option's help msg

Author: surybala

src/main/resources/com/amazonaws/codedeploy/AWSCodeDeployPublisher/help-deploymentGroupAppspec.html

@@ -1,4 +1,5 @@
 <div>
-    <p>If checked, the build will use a dedicated appspec.yml file per deployment group.<br><br>
+    <p>If checked, the build will use a dedicated appspec.yml file per deployment group.</p>
+    <p>The appspec file should be named "appspec.DEPLOYMENT_GROUP_NAME.yml" and must be present in the jenkins project workspace.</p><br><br>
     <p>e.g.: appsec.staging.yml</p>
 </div>