deps: ICU4C 63.1

[srl295]

• Subsystem: deps

62.1 was #21728 / #21452

release candidate at https://github.com/unicode-org/icu/releases/tag/release-63-rc (yes GitHub!)

[srl295]

So, it's time. http://blog.unicode.org/2018/10/icu-63-released.html

[richardlau]

@srl295 Since #23715 has landed I'm assuming this can be closed. Please reopen if I am mistaken.