Align the default case-sensitivity of `matches` with the regex default

[ReedMerrill]

matches accepts a regex for pattern matching within tidyselect functions and, in my opinion, would therefore be more user-friendly if it had the same default case-sensitivity behaviour as regex. Right now, matches is not case sensitive.

This issue proposes switching the default value of the ignore.case parameter from TRUE to FALSE. I'm happy to submit a pull request, but will wait to see how much traction this issue gets.

[ReedMerrill]

This would be a breaking change, but it would be nice if dplyr functions could behave as expected with regex.

[DavisVaughan]

At this point we don't believe we can make such a breaking change, but thanks!