Update Martinique flag (U+1F1F2-U+1F1F6)

[Jurtaa]

A new flag of Martinique was recently adopted. This pull request changes the current Martinique flag emoji to the newer version.

[jdecked]

Thanks for your submission!

We're not going to merge this right now because there's a few problems outside of a PR – people in Quebec use the Martinique flag as a stand-in for the flag of Quebec, which isn't recommended for general interchange (RGI) and thus not supported by most vendors. If we're the first emoji set to update, we may inadvertently change the meaning of people's messages cross-platform. We're planning to coordinate with other emoji vendors to see when they plan to update the Martinique flag so we can avoid inadvertent misunderstandings for users.