Update Unicode Emoji version to 12.1
The Unicode Consortium just released version 12.1 of emoji, see http://blog.unicode.org/2019/10/emoji-121-release-168-emoji-added.html.
This is unrelated to Version 12.1.0 of Unicode itself (which introduced a single new character, for 令和).
A preliminary analysis of the date files published seems to indicate that there are no new codepoints allocated (that would need an update of Unicode itself), just an increase in combinations of codepoints (skin colors, hair colors, genders,...) that are accepted as "official" emoji.
It may be that the only thing that changes for Ruby is that we have slightly more tests. If that's the case, I should be able to do the update this week, for 2.7. If it turns out that some serious work is needed for the update, we may have to delay it.