replace github link with PyPi link

[Filos1992]

Problem:
Paint is not yet registert in PyPi but is needed for ARTIST user stories. PAINT can be installed as an optional dependency with pip install ."[tutorials]"

Solution:
in project.toml it is linked with "git+ssh://git@github.com/ARTIST-Association/PAINT.git#egg=PAINT"
this should be replaced with [PAINT] when registered to pypi