[Snyk] Security upgrade nbconvert from 5.4.0 to 6.3.0b0#17

snyk-bot wants to merge 1 commit intomasterrharp/python-goof:masterfrom

snyk-fix-dac1bf9a3cf94039593a3f9be69961d2rharp/python-goof:snyk-fix-dac1bf9a3cf94039593a3f9be69961d2Copy head branch name to clipboard