Fix factories loading

[kennyadsl]

Summary

With Solidus v4.0 we don't have the factories defined in spree/testing_support anymore. Better to fetch them from the proper file that includes all the definitions.

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• [ ] I have written a thorough PR description.
• [ ] I have kept my commits small and atomic.
• [ ] I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[codecov[bot]]

Codecov Report

Merging #338 (cb37ed4) into main (e3632ae) will decrease coverage by 0.03%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #338      +/-   ##
==========================================
- Coverage   97.09%   97.06%   -0.03%     
==========================================
  Files         190      190              
  Lines        4505     4469      -36     
==========================================
- Hits         4374     4338      -36     
  Misses        131      131              

Impacted Files	Coverage Δ
template.rb	84.93% <ø> (ø)

... and 4 files with indirect coverage changes

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more