test

Don't allow recursive decoding. #214

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.5 / ubuntu-latest)	23s
build (2.5 / windows-latest)	2m 39s
build (2.6 / ubuntu-latest)	28s
build (2.6 / macos-latest)	51s
build (2.6 / windows-latest)	4m 3s
build (2.7 / ubuntu-latest)	23s
build (2.7 / macos-latest)	34s
build (2.7 / windows-latest)	2m 40s
build (3.0 / ubuntu-latest)	11s
build (3.0 / macos-latest)	17s
build (3.0 / windows-latest)	1m 26s
build (3.1 / ubuntu-latest)	13s
build (3.1 / macos-latest)	16s
build (3.1 / windows-latest)	1m 41s
build (3.2 / ubuntu-latest)	10s
build (3.2 / macos-latest)	29s
build (3.2 / windows-latest)	2m 11s
build (3.3 / ubuntu-latest)	13s
build (3.3 / macos-latest)	16s
build (3.3 / windows-latest)	2m 12s
build (head / ubuntu-latest)	13s
build (head / macos-latest)	14s
build (truffleruby-head / ubuntu-latest)	27s
build (truffleruby-head / macos-latest)	29s
build (mswin / windows-latest)	2m 0s
build (mingw / windows-latest)	1m 29s
	26m 30s

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