Fix child processes not being reaped with PID 1 #7

Job	Run time
RuboCop linting	11s
skip_duplicate_runs / Skip Duplicate Runs	5s
NON-MRI: ubuntu-22.04 jruby	2s
NON-MRI: ubuntu-22.04 jruby no SSL	3s
NON-MRI: ubuntu-22.04 jruby-head	1s
NON-MRI: ubuntu-20.04 truffleruby	4s
NON-MRI: ubuntu-20.04 truffleruby-head	2s
MRI: ubuntu-20.04 2.4	1s
NON-MRI: ubuntu-22.04 truffleruby	3s
MRI: ubuntu-20.04 2.5	2s
NON-MRI: ubuntu-22.04 truffleruby-head	3s
MRI: ubuntu-20.04 2.6	1s
NON-MRI: macos-12 jruby	4s
NON-MRI: macos-12 truffleruby	5s
MRI: ubuntu-20.04 2.7	1s
MRI: ubuntu-20.04 3.0	1s
MRI: ubuntu-20.04 3.1	1s
MRI: ubuntu-20.04 3.2	1s
MRI: ubuntu-20.04 3.3	3s
MRI: ubuntu-20.04 head	4s
MRI: ubuntu-22.04 3.1	2s
MRI: ubuntu-22.04 3.2	4s
MRI: ubuntu-22.04 3.3	1s
MRI: ubuntu-22.04 head	4s
MRI: macos-11 2.4	4s
MRI: macos-11 2.7	3s
MRI: macos-11 3.2	5s
MRI: macos-11 3.3	5s
MRI: macos-12 2.4	4s
MRI: macos-12 2.5	4s
MRI: macos-12 2.6	4s
MRI: macos-12 2.7	5s
MRI: macos-12 3.0	4s
MRI: macos-12 3.1	4s
MRI: macos-12 3.2	4s
MRI: macos-12 3.3	4s
MRI: macos-12 head	4s
MRI: macos-13 2.4	3s
MRI: macos-13 2.7	3s
MRI: macos-13 3.2	4s
MRI: macos-13 3.3	3s
MRI: windows-2022 2.4	2s
MRI: windows-2022 2.5	4s
MRI: windows-2022 2.6	4s
MRI: windows-2022 2.7	4s
MRI: windows-2022 3.0	4s
MRI: windows-2022 3.1	4s
MRI: windows-2022 3.2	2s
MRI: windows-2022 3.3	4s
MRI: windows-2022 ucrt	4s
MRI: windows-2022 mswin	2s
MRI: windows-2022 2.7 no SSL	4s
MRI: ubuntu-20.04 2.7 no SSL	2s
MRI: ubuntu-22.04 head yjit	3s
MRI: ubuntu-22.04 2.4 rack2	4s
MRI: ubuntu-22.04 3.2 rack2	8s
MRI: ubuntu-22.04 2.4 rack1	1s
	3m 12s

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