updated tutorial seed data text per issue #341

[jkoulish-bixal]

This is a simple change, very similar to the substantive fix recently merged in PR #373

Checklist

I have…

• [x] run the application locally (bin/rails server) and verified that my changes behave as expected.
• [x] run static code analysis (bin/rubocop) and vulnerability scan (bin/brakeman) against my changes.
• [x] run the test suite (bin/rake spec) and verified that all tests pass.
• [x] summarized below my changes and noted which issues (if any) this pull request fixes or addresses.
• [x] thoroughly outlined below the steps necessary to test my changes.
• [x] attached screenshots illustrating relevant behavior before and after my changes.
• [x] read, understand, and agree to the terms described in CONTRIBUTING.md.
• [x] added my name, email address, and copyright date to CONTRIBUTORS.md.

Summary of Changes

This pull request…

• Updates the text in two places on Slide #9 of the "Create a Shipment" tutorial.
• See Issue #341 for detail.
• Note: attribution already covered by @rich-allen-gov in PR #373

Testing

To verify the changes proposed in this pull request…

1. Run bundle exec rake db:reset to verify that all data was dropped, and reseeded correctly.
2. Ensure content updates appear as expected.
3. Capture changes with screenshot (below)

Screenshots

BEFORE:

AFTER: