Fix navigation mask issue with quantification of single spectrum

[ericpre]

One test added in #2602 failed on RELEASE_next_minor because when doing the quantification of a single spectrum, a navigation mask is computed automatically and clearly it shouldn't!

Progress of the PR

• Fix setting navigation_mask for the quantification of single spectrum
• add tests,
• ready for review.

[codecov]

Codecov Report

Merging #2603 (eeaabec) into RELEASE_next_minor (ec16cda) will increase coverage by 2.42%.
The diff coverage is 87.13%.

@@                  Coverage Diff                   @@
##           RELEASE_next_minor    #2603      +/-   ##
======================================================
+ Coverage               74.04%   76.47%   +2.42%     
======================================================
  Files                     197      202       +5     
  Lines                   27867    29748    +1881     
  Branches                 6037     6498     +461     
======================================================
+ Hits                    20635    22749    +2114     
+ Misses                   5521     5202     -319     
- Partials                 1711     1797      +86     

Impacted Files	Coverage Δ
hyperspy/_components/eels_arctan.py	89.47% <ø> (-1.01%)	⬇️
hyperspy/_components/voigt.py	88.88% <ø> (-0.21%)	⬇️
hyperspy/_signals/complex_signal2d.py	100.00% <ø> (ø)
hyperspy/api.py	100.00% <ø> (+50.00%)	⬆️
hyperspy/decorators.py	85.71% <ø> (+7.77%)	⬆️
hyperspy/drawing/_widgets/label.py	64.91% <ø> (ø)
hyperspy/drawing/tiles.py	0.00% <ø> (ø)
hyperspy/io_plugins/empad.py	93.54% <ø> (ø)
hyperspy/io_plugins/msa.py	75.60% <ø> (-0.30%)	⬇️
hyperspy/model.py	80.33% <ø> (+8.08%)	⬆️
... and 139 more

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[ericpre]

Doc build fails because of latest sphinx release: sphinx-doc/sphinx#8568