Use workflows to use ubuntu-latest

[Dr-Electron]

Description of change

Updated all workflows to use ubuntu-latest as 18.04 is depreciated.
Seems like #588 isn't a Problem anymore? At least python wheels were build perfectly fine in my fork.

But I'm not sure how to run the covector action and it fails for me, because it can't find iotaledger/create-pull-request

Type of change

• Bug fix (a non-breaking change which fixes an issue)

How the change has been tested

Run the python workflow in my fork

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes

[Thoralf-M]

#588 was never a problem for building, only when running something from a newer version on ubuntu 18

[Dr-Electron]

Understood. But we need to find a solution for this otherwise we can't publish the bindings for Ubuntu. And as Ubuntu 18 is basically EoL I guess it would be fine to not support it 🤔