Pull request type

• Code changes (bugfix, features)

Checklist

• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest tests -m slow --runslow) have passed locally

New behavior

Solves issue #671 .

Breaking change

• No

Additional information

From what I understood from the issue, the information required to be printed was the the ratio of the dry mass by the total mass. I saw some sources computing the propellant mass ratio, which I believe is the opposite (inverse of the specified ratio).