Whitelist the en-GB-oxendict locale name

This commit adds the Oxford English Dictionary variant (oxendict)
of the British English locale (en-GB) to the list of available
locale names.

Bug: chromium:1064659
Change-Id: I0c0a04c2224ae259932d6af642924fa4b99611c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/2119135
Reviewed-by: Frank Tang <ftang@chromium.org>
7 files changed