fix: Change IVFFlat list default to 100 (#165)

src/langchain_google_alloydb_pg/indexes.py

@@ -87,7 +87,7 @@ def to_string(self) -> str:
 @dataclass
 class IVFFlatIndex(BaseIndex):
     index_type: str = "ivfflat"
-    lists: int = 1
+    lists: int = 100
 
     def index_options(self) -> str:
         return f"(lists = {self.lists})"