Merge train checkbox text update

What does this MR do?

As an MVC for #212875 (closed), this updates the checkbox text based on the suggested style. I modified the subtext slightly to try to incorporate some of the suggestions that were brought up in the discussions.

I also had to remove the links from the suggestion, for this MVC, as links in checkbox text is complicated to get working with the specs. I think there is still a lot of benefit to to just improving the text to start. If we need to add more links, we can iterate.

Closes #212875 (closed)

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After

Does this MR meet the acceptance criteria?

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• Changelog entry
• Documentation (if required)
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• Tested in all supported browsers
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