Fix typo in notebook for 04_qaoa_variational_parameters.ipynb

[yoshioka1128]

Description

This pull request fixes a typo in the Jupyter notebook. The correction involves updating the Hamiltonian in the unitary operator definition to accurately reflect the intended equation:

• Changed from
  $$U(β_1, β_2, γ_1, γ_2) = exp(-iβ^{(2)}H_M)exp(-iγ^{(2)}H_M)exp(-iβ^{(1)}H_M)exp(-iγ^{(1)}H_M)$$

• To
  $$U(β_1, β_2, γ_1, γ_2) = exp(-iβ^{(2)}H_M)exp(-iγ^{(2)}H_C)exp(-iβ^{(1)}H_M)exp(-iγ^{(1)}H_C)$$

Checklist

• I have performed a self-review of my code.
• I have commented my code and used numpy-style docstrings
• I have made corresponding updates to the documentation.
• My changes generate no new warnings
• I have added/updated tests to make sure bugfix/feature works.
• New and existing unit tests pass locally with my changes.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

I have reviewed the changes in the 04_qaoa_variational_parameters.ipynb notebook and verified that the corrected equation is accurate. There are no additional tests required as the change is a documentation correction.