ICU-22581 Fix RBBI Leakage #1287

Job	Run time
clang-valgrind-intltest (utility)	6m 35s
clang-valgrind-intltest (normalize)	6m 14s
clang-valgrind-intltest (collator)	5m 24s
clang-valgrind-test	10m 5s
clang-valgrind-intltest (regex)	4m 59s
clang-valgrind-intltest (format)	16m 5s
clang-valgrind-intltest (translit)	5m 46s
clang-valgrind-intltest (rbbi)	6m 57s
clang-valgrind-intltest (rbnf)	6m 25s
clang-valgrind-intltest (rbnfrt)	6m 16s
clang-valgrind-intltest (icuserv)	5m 2s
clang-valgrind-intltest (idna)	5m 26s
clang-valgrind-intltest (convert)	6m 30s
clang-valgrind-intltest (rbnfp)	4m 55s
clang-valgrind-intltest (csdet)	4m 53s
clang-valgrind-intltest (spoof)	5m 14s
clang-valgrind-intltest (bidi)	5m 18s
	1h 52m 4s

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