plugins: spectral_subset choice from "None" to "Entire Spectrum"

[kecnry]

Description

This pull request updates all remaining mentions of spectral_subset = "None" in plugins to be "Entire Spectrum" for self-consistency.

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 change log needed? If yes, is it added to CHANGES.rst?
• Is a milestone set? Milestone is only currently required for PRs related to Imviz MVP.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 75.74%. Comparing base (a496fa7) to head (f902de3).
Report is 2613 commits behind head on main.

Files	Patch %	Lines
...daviz/configs/default/plugins/collapse/collapse.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1074      +/-   ##
==========================================
- Coverage   75.84%   75.74%   -0.10%     
==========================================
  Files          81       81              
  Lines        6234     6234              
==========================================
- Hits         4728     4722       -6     
- Misses       1506     1512       +6     

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[kecnry]

No new lines were added to the code, so can we please ignore the coverage warnings, please? 🥺

[javerbukh]

No controversy here, thanks!