Bump up v1.7.3 #39

Job	Run time
ruby-versions / Generate Ruby versions	7s
test (2.5, ubuntu-latest)	26s
test (2.5, macos-latest)	1m 2s
test (2.5, windows-latest)	1m 46s
test (2.6, ubuntu-latest)	43s
test (2.6, macos-latest)	1m 0s
test (2.6, windows-latest)	3m 57s
test (2.7, ubuntu-latest)	30s
test (2.7, macos-latest)	56s
test (2.7, windows-latest)	2m 17s
test (3.0, ubuntu-latest)	16s
test (3.0, macos-latest)	44s
test (3.0, windows-latest)	1m 42s
test (3.1, ubuntu-latest)	17s
test (3.1, macos-latest)	48s
test (3.1, windows-latest)	1m 6s
test (3.2, ubuntu-latest)	27s
test (3.2, macos-latest)	40s
test (3.2, windows-latest)	3m 5s
test (head, ubuntu-latest)	39s
test (head, macos-latest)	1m 2s
test (head, windows-latest)	1m 50s
test (jruby, ubuntu-latest)	5m 56s
test (jruby-head, ubuntu-latest)	5m 48s
test (truffleruby, ubuntu-latest)	2m 13s
test (truffleruby-head, ubuntu-latest)	3m 9s
	42m 26s

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