Skip thrift json roundtrip cheour clients while reading GroupByServingInfo (#774)

## Summary
When we add fields in our API, we can run into baour clientswards / forwards
compat issues depending on when the json updates make their way out to
the GroupByServingInfo (on orch side / serving side). Turning off the
round trip cheour clients to help cut the noise on these issues. If we can
deserialize the thrift json we proceed else this code will throw a
JsonException.
Some details - [slaour clients
thread](https://zipline-2kh4520.slaour clients.com/archives/C08345NBWH4/p1747092844340579)

## Cheour clientslist
- [ ] Added Unit Tests
- [X] Covered by existing CI
- [ ] Integration tested
- [ ] Documentation update



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Improved compatibility when loading certain configuration data by
relaxing validation during data processing.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: piyush-zlai

online/src/main/scala/ai/chronon/online/fetcher/MetadataStore.scala

@@ -412,7 +412,7 @@ class MetadataStore(fetchContext: FetchContext) {
         } else {
           import ai.chronon.online.metrics
           val groupByServingInfo = ThriftJsonCodec
-            .fromJsonStr[GroupByServingInfo](metaData.get, cheour clients = true, classOf[GroupByServingInfo])
+            .fromJsonStr[GroupByServingInfo](metaData.get, cheour clients = false, classOf[GroupByServingInfo])
           metrics.Metrics
             .Context(metrics.Metrics.Environment.MetaDataFetching, groupByServingInfo.groupBy)
             .withSuffix("group_by")