Update PULL_REQUEST_TEMPLATE.md changed PR template link from stable branch to latest branch.

[zeeuqsze]

PR template link was based on stable doc URL. Changed PR template link to latest branch.

Describe your changes
Updated PR template link so doc URL is based off latest branch.

Type of update
Is this a:

• Bug fix
• Update to documentation

Associated issues
Issue #918

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 #1022 (9b2fb21) into main (62a7ace) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1022   +/-   ##
=======================================
  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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