Extend m_vals range in OPI performance testing

- Add m=1, 200, 400 to test range
- Now tests m_vals = [1, 5, 10, 25, 50, 100, 200, 400]
- Shows performance across wider range of policy iteration steps

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: jstac

lectures/ifp_opi.md

@@ -356,7 +356,7 @@ print(f"Speedup factor: {vfi_time / opi_time:.2f}")
 Let's try different values of m to see how it affects performance:
 
 ```{code-cell} ipython3
-m_vals = [5, 10, 25, 50, 100]
+m_vals = [1, 5, 10, 25, 50, 100, 200, 400]
 opi_times = []
 
 for m in m_vals: