Deprecate unicode-char #17872

Job	Run time
check-deep-tests / check-deep-tests	6s
singletons	3m 23s
xunit-tests / osx	43m 55s
xunit-tests / win	21m 1s
xunit-tests / ubuntu-20.04	15m 45s
integration-tests / populate-matrix-dimensions	1s
integration-tests / test (ubuntu-20.04, 1)	17m 29s
integration-tests / test (ubuntu-20.04, 2)	20m 39s
integration-tests / test (ubuntu-20.04, 3)	19m 45s
integration-tests / test (ubuntu-20.04, 4)	16m 52s
integration-tests / test (ubuntu-20.04, 5)	18m 24s
test-coverage-analysis	58s
	2h 58m 18s

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