fix: resolve lint issues in ChunkBasedTask implementation

- Remove unused Dict import from typing
- Fix f-string without placeholders
- Remove unused imports and variables in tests

Co-Authored-By: Jo\u00E3o <joao@crewai.com>

tests/test_chunk_based_task_integration.py

@@ -1,4 +1,3 @@
-import pytest
 import tempfile
 from pathlib import Path
 
@@ -42,7 +41,7 @@ class TestChunkBasedTaskIntegration:
                 agent=agent
             )
             
-            crew = Crew(
+            Crew(
                 agents=[agent],
                 tasks=[task],
                 memory=True