Tutorial update vis nir

[HaleySchuhl]

Describe your changes
Updates to plantcv docs pages that point to the updated tutorial for a dual VIS/NIR workflow.

Type of update
Is this a:

• Collaboration with @leowlima who did all the leg work of building a new GitHub repo and updating the actual tutorial to v4 syntax. Thanks!!!
• Update to documentation

Associated issues
#1293

Additional context
Add any other context about the problem here.

For the reviewer
See this page for instructions on how to review the pull request.

• PR functionality reviewed in a Jupyter Notebook
• All tests pass
• Test coverage remains 100%
• Documentation tested
• New documentation pages added to plantcv/mkdocs.yml
• Changes to function input/output signatures added to updating.md
• Code reviewed
• PR approved

[codecov]

Codecov Report

Merging #1301 (48ea65b) into release-4.0 (5cc1a25) will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           release-4.0     #1301   +/-   ##
=============================================
  Coverage       100.00%   100.00%           
=============================================
  Files              157       157           
  Lines             6759      6759           
=============================================
  Hits              6759      6759           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

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