Fix false positives on Iron browser for Iron-model devices.

[JBYoshi]

Description:

Devices with "Iron" in their brand names were originally being incorrectly detected as running the Iron browser. This PR makes one of the two Iron browser regexes more strict to avoid those false positives.

The two regexes now check for either the "Chrome/" token followed by an "Iron" token or for an "Iron/" token, with the slash. There are existing test cases covering both of those cases (Chrome/ Iron case, Iron/ case). I cross-checked the patterns with https://user-agents.net/download?browser_type=browser&browser=iron to make sure there weren't any other patterns used by the Iron browser.

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