ci(nightly): correct actions/checkout version tag

[erisu]

Platforms affected

n/a

Motivation and Context

Fix incorrect actions/checkout version tag.

Description

Changed actions/checkout@3 to actions/checkout@v3

Testing

n/a

Checklist

• [ ] I've run the tests to see all new and existing tests pass
• [ ] I added automated test coverage as appropriate for this change
• [ ] Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• [ ] If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• [ ] I've updated the documentation if necessary

[codecov-commenter]

Codecov Report

Merging #304 (ff1f033) into master (76020ea) will decrease coverage by 1.83%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #304      +/-   ##
==========================================
- Coverage   58.73%   56.91%   -1.83%     
==========================================
  Files           8        8              
  Lines         492      492              
==========================================
- Hits          289      280       -9     
- Misses        203      212       +9     

Impacted Files	Coverage Δ
src/repoutil.js	68.91% <ø> (ø)

... and 1 file with indirect coverage changes

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