math/py-matplotlib-scalebar: Update to 0.8.1

• Correct license to BSD, like done in sources
• Remove useless shebangs

Changelog: https://github.com/ppinard/matplotlib-scalebar/compare/0.8.0...0.8.1

Reported by: Repology

MFH: 2022Q1
(cherry picked from commit adf59b180ce26d6d376049be9e37774fefc6371d)