Bump actions/checkout from 3 to 4 #144

Job	Run time
Test coverage	20s
Confirm config and documentation	18s
Edge RuboCop: internal_investigation	14s
Edge RuboCop: spec	17s
RSpec 4	16s
Ruby 2.7: internal_investigation	33s
Ruby 2.7: spec	35s
Ruby 3.0: internal_investigation	16s
Ruby 3.0: spec	20s
Ruby 3.1: internal_investigation	17s
Ruby 3.1: spec	20s
Ruby 3.2: internal_investigation	17s
Ruby 3.2: spec	22s
Ruby ruby-head: internal_investigation	14s
Ruby ruby-head: spec	17s
Ruby jruby-9.4: internal_investigation	1m 8s
Ruby jruby-9.4: spec	1m 11s
	7m 15s

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