Fix python import in MemoryDB client

The incorrect import is a result of previous duplicate import of the same class name and recent refactoring.
032515f#diff-1638e273a6d7eee7b4412bf79bda9112da86d53e18d1b650b8b80a2e1df4f7e6R15

Author: ChristophKoerner

vectordb_bench/backend/clients/memorydb/memorydb.py

@@ -9,10 +9,10 @@
 from redis import Redis
 from redis.cluster import RedisCluster
 from redis.commands.search.field import NumericField, TagField, VectorField
-from redis.commands.search.indexDefinition import IndexDefinition
+from redis.commands.search.indexDefinition import IndexDefinition, IndexType
 from redis.commands.search.query import Query
 
-from ..api import IndexType, VectorDB
+from ..api import VectorDB
 from .config import MemoryDBIndexConfig
 
 log = logging.getLogger(__name__)