deps: update icu to 78.1 #726

Job	Run time
Build slim tarball	1m 32s
x86_64-linux: with shared libraries	28m 56s
aarch64-linux: with shared libraries	23m 53s
x86_64-darwin: with shared libraries	40m 54s
aarch64-darwin: with shared libraries	22m 56s
	1h 58m 11s

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