THRIFT-5425 Throw an exception when reading TSimpleJson in Java

[thomasbruggink]

Client java

Throw an exception when reading TSimpleJson and update the comment
explain why.

I'm wondering if just throwing is acceptable since this will break backwards compatibility with clients that actually try to read. Let me know if just updating the comment would be a better solution.

• Did you create an Apache Jira ticket? (not required for trivial changes)
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit? (not required, but preferred)
• Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.

[Jens-G]

+1 Looks reasonable to me, I'm for it.