community[patch]: pgvector replace nin_ by not_in (#22619)

- [ ] **community**: "pgvector: replace nin_ by not_in"

- [ ] **PR message**: nin_ do not exist in sqlalchemy orm, it's not_in

libs/community/langchain_community/vectorstores/pgvector.py

@@ -733,7 +733,7 @@ class PGVector(VectorStore):
             if operator in {"$in"}:
                 return queried_field.in_([str(val) for val in filter_value])
             elif operator in {"$nin"}:
-                return queried_field.nin_([str(val) for val in filter_value])
+                return queried_field.not_in([str(val) for val in filter_value])
             elif operator in {"$like"}:
                 return queried_field.like(filter_value)
             elif operator in {"$ilike"}: