Minors changes for JOSS paper

[JanJereczek]

This PR includes following minor changes:

• My second affiliation has been removed
• /paper has been excluded from codecov, which should largely address Increase test coverage to at least 85% #64
• The abstracts have been removed from paper.bib
• The url link for the documentation in paper.md has been fixed

[Datseris]

it is a waste of computational resources to constantly build the PDF of the paper in every single PR. Let's please remove the draft-pdf workflow once you have managed to build the paper once.

[JanJereczek]

Yes, I think we already agreed on removing the pdf build action as soon as the paper is published!

[JanJereczek]

Documentation is not built properly because of a change in the interplay between trajectory and obtain_state in DynamicalSystemsBase.jl (used in logisitc example of the docs).

[Datseris]

Fixed in JuliaDynamics/DynamicalSystemsBase.jl#201

@JanJereczek , some advice for the future. If you have found an error, paste it. Don't just say "this error happened", copy the error message and paste it. Or alternatively copy the CI log line that has the error if you don't want to paste the entire thing. Let's not duplicate the effort to find the bug, which in some cases like now is trivial, but in general is non zero.

[JanJereczek]

Thanks for fixing it @Datseris. The PR should be ready to merge! You are right, I will include the error messages in future :)