Exclude .paypal.com as referrer by default #19516

Description:

As requested by @mattab

Adds .paypal.com to the default list of excluded referrers in javascript tracker.
If someone calls setExcludedReferrers in his tracking code, this will be overwritten.

Note: This will not exclude PayPal as referrer on PHP site by default. But that shouldn't be needed if the javascript tracker doesn't send the referrer anymore.

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] 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