The log message is a standard deprecation notice from Amazon Web Services. It's telling you that the tool Mendix uses to communicate with your S3 bucket (the AWS SDK for Java v1.x) is being phased out.
Think of it like a warning that your phone's operating system will no longer be supported next year. The phone works fine today, but it will become a security risk and might lose compatibility with new apps in the future.
The stack trace you provided is key. Lines like com.mendix.storage.s3.internal.ClientProvider show that this code is part of the Mendix platform's built-in S3 connector, not your custom application logic.
This means Mendix is responsible for upgrading the AWS SDK in a future release of the platform. Your responsibility is to upgrade your Mendix application to that newer version before the deadline.