[Issue-2816] - Update exception type in JsonDeserializer to JsonSyntaxException

[Shershah03]

…xException

Purpose

Closes #2816

Description

As mentioned in #2816 , If _com.google.gson.Gson.fromJson(String, Class<User>)_ throws JsonSyntaxException but in case any one imeplements custom JsonDeserializer then it by default throws JsonParseException.
For any com.google.gson.Gson.fromJson(String, Class<User>) calls , its normal to catch JsonSyntaxException, But in case use of JsonDeserializer, this exception will not be caught.
Ideally fromJson and JsonDeserializer interface should throw same exceptions.

Checklist

• New code follows the Google Java Style Guide
  This is automatically checked by mvn verify, but can also be checked on its own using mvn spotless:check.
  Style violations can be fixed using mvn spotless:apply; this can be done in a separate commit to verify that it did not cause undesired changes.
• If necessary, new public API validates arguments, for example rejects null
• New public API has Javadoc
  • Javadoc uses @since $next-version$
    ($next-version$ is a special placeholder which is automatically replaced during release)
• If necessary, new unit tests have been added
  • Assertions in unit tests use Truth, see existing tests
  • No JUnit 3 features are used (such as extending class TestCase)
  • If this pull request fixes a bug, a new test was added for a situation which failed previously and is now fixed
• mvn clean verify javadoc:jar passes without errors

[Shershah03]

Can someone approve the PR please?

[Marcono1234]

Thanks for this pull request! I am however not sure if it might be better to instead change the signature of the Gson#fromJson methods to mention that they can throw a JsonParseException, see #2816 (comment).