UTF8 codepoint -> Unicode codepoint in regex docs

[BurntSushi]

Bug report by proxy from reddit. Documentation should say Unicode codepoints, but it currently says UTF8 codepoints. e.g.,

"This implementation executes regular expressions only on sequences of UTF8 codepoints while exposing match locations as byte indices into the search string."

"Regular expressions themselves are also only interpreted as a sequence of UTF8 codepoints. This means you can embed use Unicode characters directly into in your expression:"