Tags are formatted wrong for the custom metric

[VitoMakarevich]

Here I created an issue and investigated it. DataDog/datadog-lambda-extension#57
In short, this code is incorrect https://github.com/DataDog/datadog-lambda-java/blob/main/src/main/java/com/datadoghq/datadog_lambda_java/MetricWriter.java#L64
The repl example is https://replit.com/@VitaliyMakarevi/PepperyAgileMatrix#Main.java
So as you could see, the logs are concatenated without commas using StringBuilder, could someone create a patch & make a new release with the fix?

[IvanTopolcic]

Fixed in v1.4.4. Thanks so much for your contribution, we really appreciate it!