Clean up the gitignore file

[eskultety]

When cachi2 was created out of cachito as a replacement with a different approach, the code base essentially started copied over and has been changed over the years. There are still files lurking in our code base hosting content from the cachito origin which either don't apply at all or require tweaks to get rid of our ties and references to the old project.
One of such examples is the .gitignore file which lists patterns for services (e.g. Celery, Jupyter, Spyder, etc.) along with patterns filtering out temporary files created by various code editors and IDEs. All of those should be cleaned up as only strictly project-related artifacts (build or CI/CD artifacts) should be ignored by the project-level git ignore file. Especially with the latter group these should be left for individual contributors to put in their global .gitignore file so that the settings are applied to all of their projects rather than per-project and forcing a particular upstream to adopt unrelated patterns.