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[bot]]

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

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

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