[Fix] incorrect ascension level in givechar command

[gentlespoon]

1. Characters <= Lv.20 should never be asc 1.
2. Make Lv.20 asc 0 to allow testing with lv 20 characters without asc. Might be useful for testing world-level increase and other scenarios. People who give themselves characters <= lv90 clearly know what they want, also asc 1 is just one click away, so it should be fine. Same for other levels.

Type of changes

• Bug fix
• New feature
• Enhancement
• Documentation

Checklist:

• My code follows the style guidelines of this project
• My pull request is unique and no other pull requests have been opened for these changes
• I have read the Contributing note and Code of conduct
• I am responsible for any copyright issues with my code if it occurs in the future.