use composer/ca-bundle for default CA bundle #16797

As mentioned in https://github.com/matomo-org/matomo/pull/13743#issuecomment-441435508 a long time ago.

This should not change anything as composer/ca-bundle was already an indirect dependency.

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

I've rebased the branch and resolved the conflicts. Should imho be good to merge now