Fix duplicate import and verify notebook correctness

Remove duplicate 'import dspy' from cell 20 (already imported in cell 2).

Comprehensive verification completed:
✅ All markdown headers properly aligned with code cells
✅ All imports present and non-duplicated
✅ All variables defined in correct order
✅ Code flow is logical and sequential
✅ No syntax errors or undefined references
✅ Function definitions have proper type hints and docstrings

Notebook structure:
- Installation and Setup (cells 1-2)
- Language Model Configuration (cells 3-4)
- Dataset Loading and Filtering (cells 5-9)
- Dataset Preparation Functions (cells 10-14)
- Baseline Chain-of-Thought Program (cells 15-16)
- Evaluation Metric (cells 17-18)
- Baseline Evaluation (cells 19-20)
- GEPA Optimization (cells 21-25)
- Optimized Program Evaluation (cells 26-27)

The notebook is now ready for production use with no bugs or alignment issues.

Author: behroozazarkhalili