Moving solidus_sample to be development dependency

[softr8]

Summary

Solidus Sample gem includes seed data to setup local development in an easy way, it includes catalogs for countries, states, products, taxonomies/taxons and images. This gem itself needs about 10mb of disk space and most of the times it is only needed in local development or one time.

Example

~ $ du -a /app/vendor/bundle/ruby/2.7.0/gems/ 2>/dev/null | sort -n -r | head -n 100
363848	/app/vendor/bundle/ruby/2.7.0/gems/
...
9696	/app/vendor/bundle/ruby/2.7.0/gems/solidus_sample-2.11.15
9648	/app/vendor/bundle/ruby/2.7.0/gems/solidus_sample-2.11.15/db
9640	/app/vendor/bundle/ruby/2.7.0/gems/solidus_sample-2.11.15/db/samples

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

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (64f6a58) 88.66% compared to head (6eb253e) 88.65%. Report is 6 commits behind head on main.

Files	Patch %	Lines
...ib/generators/solidus/install/install_generator.rb	33.33%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5591      +/-   ##
==========================================
- Coverage   88.66%   88.65%   -0.02%     
==========================================
  Files         683      683              
  Lines       16293    16296       +3     
==========================================
+ Hits        14446    14447       +1     
- Misses       1847     1849       +2     

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