example: switch the postgres source example to use change notification (#956)

Author: georgeh0

examples/postgres_source/main.py

@@ -63,8 +63,8 @@ def postgres_product_indexing_flow(
             ),
             # Optional.
             ordinal_column="modified_time",
+            notification=cocoindex.sources.PostgresNotification(),
         ),
-        refresh_interval=datetime.timedelta(seconds=30),
     )
 
     indexed_product = data_scope.add_collector()

examples/postgres_source/pyproject.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 description = "Demonstrate how to use Postgres tables as the source for CocoIndex."
 requires-python = ">=3.11"
 dependencies = [
-    "cocoindex[embeddings]>=0.2.1",
+    "cocoindex[embeddings]>=0.2.3",
     "python-dotenv>=1.0.1",
     "pgvector>=0.4.1",
     "psycopg[binary,pool]",