Hide Centroid Redshift when lines aren't loaded

[duytnguyendtn]

Description

This PR incorporates user feedback that the Redshfit from Centroid section from the Line Analysis plugin should only be shown if lines are actually plotted.

Because this is a UI element, coverage is expected to decrease

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a milestone set? Set this to bugfix milestone if this is a bug fix and needs to be released ASAP; otherwise, set this to the next major release milestone.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Patch coverage: 76.55% and project coverage change: +0.01 🎉

Comparison is base (d261e71) 90.91% compared to head (388430c) 90.92%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2294      +/-   ##
==========================================
+ Coverage   90.91%   90.92%   +0.01%     
==========================================
  Files         152      152              
  Lines       17028    17115      +87     
==========================================
+ Hits        15481    15562      +81     
- Misses       1547     1553       +6     

Impacted Files	Coverage Δ
...igs/default/plugins/model_fitting/model_fitting.py	86.45% <ø> (ø)
...imviz/plugins/aper_phot_simple/aper_phot_simple.py	92.66% <ø> (ø)
...igs/specviz/plugins/line_analysis/line_analysis.py	97.05% <ø> (ø)
jdaviz/core/data_formats.py	76.53% <33.33%> (-1.85%)	⬇️
jdaviz/core/launcher.py	35.18% <37.50%> (+19.56%)	⬆️
jdaviz/cli.py	27.90% <50.00%> (+0.84%)	⬆️
jdaviz/__init__.py	88.23% <100.00%> (ø)
jdaviz/components/toolbar_nested.py	85.00% <100.00%> (+11.31%)	⬆️
jdaviz/configs/imviz/plugins/tools.py	92.72% <100.00%> (+0.13%)	⬆️
...daviz/configs/imviz/tests/test_simple_aper_phot.py	100.00% <100.00%> (ø)
... and 3 more

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[kecnry]

Awesome - thanks!