Bump nbconvert from 6.2.0 to 6.3.0 in /tools/qubot
Bump nbconvert from 6.2.0 to 6.3.0 in /tools/qubot

Bumps [nbconvert](https://github.com/jupyter/nbconvert) from 6.2.0 to 6.3.0.
- [Release notes](https://github.com/jupyter/nbconvert/releases)
- [Commits](https://github.com/jupyter/nbconvert/compare/6.2.0...6.3.0)

---
updated-dependencies:
- dependency-name: nbconvert
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
cksystemsteaching/selfie,cksystemsteaching/selfie,cksystemsteaching/selfie