Tests

Remove custom_specs override. #1406

Job	Run time
test (ruby=2.7)	18s
test (ruby=2.7, concurrency=async-websocket)	19s
test (ruby=3.0)	17s
test (ruby=3.1)	16s
test (ruby=3.2)	23s
test (ruby=3.3)	24s
test (ruby=ruby-head)	23s
test (ruby=jruby-head)	19s
coveralls	0s
	2m 39s

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