fix: remove non-existent storage kwargs in E2E tests

Why this change is needed:
E2E tests were failing with TypeError because they used non-existent
parameters kv_storage_cls_kwargs, graph_storage_cls_kwargs, and
doc_status_storage_cls_kwargs. These parameters do not exist in
LightRAG's __init__ method.

How it solves it:
Removed the three non-existent parameters from all LightRAG initializations
in test_e2e_multi_instance.py:
- test_legacy_migration_postgres
- test_multi_instance_postgres (both instances A and B)

PostgreSQL storage classes (PGKVStorage, PGGraphStorage, PGDocStatusStorage)
use ClientManager which reads configuration from environment variables
(POSTGRES_HOST, POSTGRES_PORT, etc.) that are already set in the E2E
workflow, so no additional kwargs are needed.

Impact:
- Fixes TypeError on LightRAG initialization
- E2E tests can now properly instantiate with PostgreSQL storages
- Configuration still works via environment variables

Testing:
Next E2E run should successfully initialize LightRAG instances
and proceed to actual migration/multi-instance testing.

tests/test_e2e_multi_instance.py

@@ -265,9 +265,6 @@ async def test_legacy_migration_postgres(
                 **pg_config,
                 "cosine_better_than_threshold": 0.8
             },
-            kv_storage_cls_kwargs=pg_config,
-            graph_storage_cls_kwargs=pg_config,
-            doc_status_storage_cls_kwargs=pg_config,
         )
 
         print("🔄 Initializing LightRAG (triggers migration)...")
@@ -496,9 +493,6 @@ async def test_multi_instance_postgres(
             **pg_config,
             "cosine_better_than_threshold": 0.8
         },
-        kv_storage_cls_kwargs=pg_config,
-        graph_storage_cls_kwargs=pg_config,
-        doc_status_storage_cls_kwargs=pg_config,
     )
 
     await rag_a.initialize_storages()
@@ -520,9 +514,6 @@ async def test_multi_instance_postgres(
             **pg_config,
             "cosine_better_than_threshold": 0.8
         },
-        kv_storage_cls_kwargs=pg_config,
-        graph_storage_cls_kwargs=pg_config,
-        doc_status_storage_cls_kwargs=pg_config,
     )
 
     await rag_b.initialize_storages()