x/supply: use internal package

[fedekunze]

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: clog add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #4661 into master will increase coverage by <.01%.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##           master    #4661      +/-   ##
==========================================
+ Coverage   54.78%   54.78%   +<.01%     
==========================================
  Files         269      269              
  Lines       16907    16917      +10     
==========================================
+ Hits         9262     9268       +6     
- Misses       6963     6967       +4     
  Partials      682      682

[alexanderbez]

ACK