Remove no longer shipped example plugins during update #16858

Description:

fix https://github.com/matomo-org/matomo/issues/16857

this affects basically all example plugins that have a version constraint defined in their plugin.json. However, it is better to remove all of them because eventually these plugins will become incompatible (as we stopped shipping them at some point during Matomo 3.X).

Review

• [ ] Functional review done
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done see checklist
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed