Minor fixes for 0.38

[mudit2812]

Minor changes for QA for 0.38:

• Trailing whitespace removed from changelog
• Change qml.cond's docs to stop using np.array(<value>, requires_grad=True) as np should be vanilla numpy, not autograd. Additionally, the use of pennylane.numpy does not add anything meaningful to the examples in the docs.
• I also also added a note to the qml.cond docs about falling back to python control flow when qml.qjit is not active.
• Fix whitespace in LinearCombination docs.
• Fix formatting and type hints in docs for functions related to group_observables.
• Add license note to diagonalize_measurements and wrap some stuff in inline code blocks in the doc string.
• Minor doc fix to single_qubit_fusion.
• Minor formatting and code correction to split_to_single_terms's docstring
• Minor doc fix for qml.UCCSD.
• Squeeze batch dimension of inputs to a function given as input to qml.fourier.coefficients. The squeezing was being done by broadcast_expand before, which is no longer the case.

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (v0.38.0-rc0@020d56f). Learn more about missing BASE report.

Additional details and impacted files

@@              Coverage Diff               @@
##             v0.38.0-rc0    #6163   +/-   ##
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  Coverage               ?   99.66%           
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  Files                  ?      445           
  Lines                  ?    42358           
  Branches               ?        0           
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  Hits                   ?    42216           
  Misses                 ?      142           
  Partials               ?        0           

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