Fix streaming functions for LegacySNSMessage (#324) (#350)

Signed-off-by: Ashish Agrawal <ashisagr@amazon.com>

Signed-off-by: Ashish Agrawal <ashisagr@amazon.com>
(cherry picked from commit 84b4ee3)

Co-authored-by: Ashish Agrawal <ashisagr@amazon.com>

Author: opensearch-trigger-bot[bot]

src/main/java/org/opensearch/commons/destination/message/LegacySNSMessage.java

@@ -57,8 +57,8 @@ private LegacySNSMessage(
 
     public LegacySNSMessage(StreamInput streamInput) throws java.io.IOException {
         super(streamInput);
-        this.subject = streamInput.readString();
         this.message = super.getMessageContent();
+        this.subject = streamInput.readString();
         this.roleArn = streamInput.readString();
         this.topicArn = streamInput.readString();
         this.clusterName = streamInput.readString();
@@ -148,7 +148,6 @@ public String getClusterName() {
     public void writeTo(StreamOutput streamOutput) throws IOException {
         super.writeTo(streamOutput);
         streamOutput.writeString(subject);
-        streamOutput.writeString(message);
         streamOutput.writeString(roleArn);
         streamOutput.writeString(topicArn);
         streamOutput.writeString(clusterName);