test

Use grouping instead of generic_symbol #506

Job	Run time
test-memory (head)	30s
steep-check (head)	13s
test-ruby (head, master)	6m 3s
check-misc (head)	8s
test-ruby (3.0, master)	6m 19s
test-windows (head)	1m 51s
ruby-versions / Generate Ruby versions	2s
test-cpp (head, g++)	14s
test (2.5)	25s
test-cpp (head, clang++)	17s
test (2.6)	25s
test (2.7)	25s
test (3.0)	12s
test (3.1)	13s
test (3.2)	12s
test (3.3)	12s
test (head)	11s
	17m 52s

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