hello_world_plugin: fix find version variables

[scpeters]

🦟 Bug fix

Fixes version numbers in anticipation of the next round of version bumps.

Summary

Use *_VERSION_MAJOR variables to aid search/replace scripts.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[codecov]

Codecov Report

Merging #607 (e0a265a) into main (35d87f3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #607   +/-   ##
=======================================
  Coverage   53.60%   53.60%           
=======================================
  Files         214      214           
  Lines       21355    21355           
=======================================
  Hits        11448    11448           
  Misses       9907     9907           

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