Remove redundant alpha parameter in cake_eating_egm

The α parameter doesn't need to be passed explicitly to create_model
since it already has a default value of 0.4. The α = 0.4 line is still
needed for the lambda function closures (f and f_prime capture it).

Changed:
- create_model(u=u, f=f, α=α, ...)
+ create_model(u=u, f=f, ...)

Tested successfully with same convergence behavior.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: jstac

lectures/cake_eating_egm.md

@@ -273,7 +273,7 @@ u_prime_inv = lambda x: 1 / x
 f = lambda k: k**α
 f_prime = lambda k: α * k**(α - 1)
 
-model = create_model(u=u, f=f, α=α, u_prime=u_prime,
+model = create_model(u=u, f=f, u_prime=u_prime,
                      f_prime=f_prime, u_prime_inv=u_prime_inv)
 s_grid = model.s_grid
 ```