remove extra dependencies and make AbstractStream no longer experimental

Author: brianjlai

airbyte_cdk/sources/declarative/concurrent_declarative_source.py

@@ -16,7 +16,6 @@
     Mapping,
     Optional,
     Set,
-    Union,
 )
 
 import orjson

airbyte_cdk/sources/streams/concurrent/abstract_stream.py

@@ -14,10 +14,6 @@
 from airbyte_cdk.sources.streams.concurrent.partitions.partition import Partition
 
 
-@deprecated(
-    "This class is experimental. Use at your own risk.",
-    category=ExperimentalClassWarning,
-)
 class AbstractStream(ABC):
     """
     AbstractStream is an experimental interface for streams developed as part of the Concurrent CDK.