Remove an erroneous assert #12407

Job	Run time
ruby-bench (--warmup=1 --bench=1 --excludes=lobsters)	15m 46s
make (check, i686)	12m 6s
make (check, ubuntu-24.04, capi)	10m 18s
make (check, --disable-yjit)	8m 13s
make (check, cppflags=-DVM_CHECK_MODE)	8m 49s
make (test-bundler-parallel, 50)	23m 31s
make (check, --enable-shared --enable-load-relative)	7m 55s
make (test-bundled-gems)	21m 14s
make-ibm	0s
Ubuntu result	3s
	1h 47m 55s

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