Remove hf dependency in qubit tapering

[obliviateandsurrender]

Context:
This PR removes the dependency of _generate_qubit_operator from the hf module. It also adds a consistency check to manually add wires to the tapered observable if some go missing due to the simplify() routine.

Description of the Change:

1. Replaces _generate_qubit_operator from hf module with the jordan_wigner from unified qchem module.
2. Adds consistency check for tapered wires inqml.taper. This allows us to return consistent observables in the case of tapering of non-Hamiltonian observables.
3. Replaced the test_hf_energy unittest with a newer test_taper_obs unittest that uses the above consistency check.
4. Fix a minor documentation issue with jordan_wigner.

Benefits:
Removes dependency for the deprecated hf module and addresses wires consistency issue with empty simplified tapered observables.

Possible Drawbacks:
None.

Related GitHub Issues:
None.

[github-actions]

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[codecov]

Codecov Report

Merging #2510 (a46628d) into master (58666c8) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2510      +/-   ##
==========================================
- Coverage   99.47%   99.47%   -0.01%     
==========================================
  Files         244      244              
  Lines       19427    19423       -4     
==========================================
- Hits        19325    19321       -4     
  Misses        102      102              

Impacted Files	Coverage Δ
pennylane/qchem/observable_hf.py	100.00% <ø> (ø)
pennylane/qchem/tapering.py	100.00% <100.00%> (ø)

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[soranjh]

Thanks @obliviateandsurrender, looks good to me, just left few comments and suggestions.

[antalszava]

Coverage checks out, overriding the check.