Update documentation of quantum_fisher

[dwierichs]

Context:
The documentation of qinfo.quantum_fisher was not quite precise on when adjoint_metric_tensor is being used (successfully), and did not mention potential auxiliary wire requirements.

Description of the Change:
Make the criterion on using default.qubit precise (because we catch other devices), and mention that for other settings, an auxiliary wire may be required.

Benefits:

Possible Drawbacks:

Related GitHub Issues:
#6059
[sc-70300]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.66%. Comparing base (0ffd5d0) to head (ddc9bc8).
Report is 294 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6074      +/-   ##
==========================================
- Coverage   99.66%   99.66%   -0.01%     
==========================================
  Files         430      430              
  Lines       41786    41489     -297     
==========================================
- Hits        41648    41349     -299     
- Misses        138      140       +2     

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