Fixing dismatch between dense matrix() and sparse repr sparse_matrix() of GlobalPhase

[JerryChen97]

Context:
qml.GlobalPhase does not set its hyperparameters during initialization. This caused certain bugs, e.g.

>>> np.allclose(qml.GlobalPhase(0.123).matrix(), qml.GlobalPhase(0.123).sparse_matrix().toarray())
False
>>> qml.GlobalPhase(0.123).matrix().shape
(1, 1)
>>> qml.GlobalPhase(0.123).sparse_matrix().shape
(2, 2)
>>> qml.GlobalPhase(0.123).matrix()
array([[0.99244503-0.12269009j]])
>>> qml.GlobalPhase(0.123).sparse_matrix().toarray()
array([[0.99244503-0.12269009j, 0.        +0.j        ],
       [0.        +0.j        , 0.99244503-0.12269009j]])

where GlobalPhase.sparse_matrix() did the calculation wrongly because it never received correct n_wires from hyperparameters, which is required by the base class Operator

Description of the Change:

Benefits:

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 99.59%. Comparing base (a7514b7) to head (5c045e6).

Files with missing lines	Patch %	Lines
pennylane/math/matrix_manipulation.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6940      +/-   ##
==========================================
- Coverage   99.59%   99.59%   -0.01%     
==========================================
  Files         480      480              
  Lines       45510    45516       +6     
==========================================
+ Hits        45325    45330       +5     
- Misses        185      186       +1     

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[JerryChen97]

It seems that the line119 has never been visited by the whole codebase. This means it actually only serves for the previous wrong impelmentation of GlobalPhase(.., wires=None). So we will just delete this