Remove GC.compact from the benchmark harness #1745

Job	Run time
benchmark-graph	47s
test (ruby)	48s
benchmark-default (ruby)	14m 11s
benchmark-default (truffleruby, --excludes=knucleotide,lobsters,ruby-lsp,shipit)	13m 5s
test (head)	51s
test (truffleruby)	1m 47s
benchmark-default (head)	13m 15s
benchmark-ractor (head)	8m 39s
benchmark-ractor-only (head)	39s
benchmark-run-once	1m 40s
all-tests	3s
	55m 45s

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