Update print to plot gaussian_blur.md

[leowlima]

Describe your changes
A clear and concise description of what changes are made by this pull request.
What was the previous functionality (if relevant) and what can we do now with
these changes.

Type of update
Is this a:

• Update to documentation

Associated issues
Issues #999

Additional context
Changed "print" to "plot" in

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 #1026 (14d4ab5) into main (234229d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1026   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         141      141           
  Lines        6004     6004           
=======================================
  Hits         6003     6003           
  Misses          1        1           

Flag	Coverage Δ
unittests	99.98% <ø> (ø)

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