[SEDONA-139] Fix wrong argument order in Flink unit tests

[sekikn]

Did you read the Contributor Guide?

• Yes, I have read Contributor Rules and Contributor Development Guide

Is this PR related to a JIRA ticket?

• Yes, the URL of the assoicated JIRA ticket is https://issues.apache.org/jira/browse/SEDONA-139. The PR name follows the format [SEDONA-XXX] my subject.

What changes were proposed in this PR?

• This PR fixes the argument order passed to JUnit's assert methods so that developers doesn't get confused.

How was this patch tested?

• Ran mvn test -pl flink locally and ensured all tests passed.

Did this PR include necessary documentation updates?

• No, this PR does not affect any public API so no need to change the docs.