Fix deserialization for PutSynonymResponse

[GeorgeCiachir]

The ReloadResult should be a member of the PutResponseSynonym, instead of the ReloadDetails, so that the PutResponseSynonym is properly serialized.
Current behavior is that it throws a MissingRequiredPropertyException

This PR fixes elastic/elasticsearch-java#784

[cla-checker-service]

❌ Author of the following commits did not sign a Contributor Agreement:
73d60cc

Please, read and sign the above mentioned agreement if you want to contribute to this project

[pquentin]

Hello! Your commit does not have an email attached to it, as can be seen here: https://github.com/elastic/elasticsearch-specification/commit/73d60cc69eebf71eb97b34fdd29c2aa091cc16d3.patch. You can also see it with git show on the command line.

You should use the email address you used to sign the CLA instead. See https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-personal-account-on-github/managing-email-preferences/setting-your-commit-email-address#setting-your-commit-email-address-in-git for how to setup your email address in git. You will then need to edit your commit or create a new one, as you prefer.

[GeorgeCiachir]

Hi, @pquentin !

Thanks for the comment.
Didn't realize the issue. I created another PR, because I accidentally closed this one.
The new PR is: #2577