Fix engine detection on old Qwant iOS versions.

[JBYoshi]

Description:

Until just this week, all browsers on iOS were required to use WebKit. However, I saw that a test case for the Qwant browser on iOS was incorrectly being detected as using the Gecko engine. This PR updates the QwantMobile token detection to allow for different engines.

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