Set restart_heaps to false after sweep thread wakeup #12901

Job	Run time
ruby-bench (--warmup=1 --bench=1 --excludes=shipit)	14m 34s
make (test-bundler-parallel, 50)	19m 31s
make (check, cppflags=-DVM_CHECK_MODE)	5m 13s
make (check, --enable-shared --enable-load-relative)	4m 53s
make (check, ubuntu-24.04, capi)	5m 15s
make (check, --disable-yjit)	4m 7s
make (test-bundled-gems)	12m 48s
make (check, i686)	3m 41s
make-ibm	0s
Ubuntu result	3s
	1h 10m 5s

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