Deprecate print results

[nfahlgren]

Describe your changes
Finishes deprecating pcv.print_results by removing the files and updating the references in the docs to pct.outputs.save_results.

Type of update
Is this a: update

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 #1327 (372c03d) into release-4.0 (f2eebed) will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           release-4.0     #1327   +/-   ##
=============================================
  Coverage       100.00%   100.00%           
=============================================
  Files              157       156    -1     
  Lines             6777      6772    -5     
=============================================
- Hits              6777      6772    -5     

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

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
plantcv/plantcv/__init__.py	100.00% <ø> (ø)

... and 1 file with indirect coverage changes