Bump syn from 2.0.18 to 2.0.28 #467

Job	Run time
oxi-test (ruby=2.7, os=ubuntu-latest)	1m 43s
oxi-test (ruby=3.2, os=ubuntu-latest)	1m 16s
oxi-test (ruby=ruby-head, os=ubuntu-latest)	1m 41s
oxi-test (ruby=2.7, os=windows-latest)	5m 16s
oxi-test (ruby=3.2, os=windows-latest)	7m 15s
oxi-test (ruby=ruby-head, os=windows-latest)	8m 3s
oxi-test (ruby=2.7, os=macos-latest)	3m 1s
oxi-test (ruby=3.2, os=macos-latest)	2m 3s
oxi-test (ruby=ruby-head, os=macos-latest)	2m 25s
magnus-0.5 (ruby=2.7, os=ubuntu-latest)	2m 45s
magnus-0.5 (ruby=3.2, os=ubuntu-latest)	2m 46s
magnus-0.5 (ruby=ruby-head, os=ubuntu-latest)	3m 24s
magnus-0.5 (ruby=2.7, os=windows-latest)	10m 52s
magnus-0.5 (ruby=3.2, os=windows-latest)	9m 6s
magnus-0.5 (ruby=2.7, os=macos-latest)	3m 54s
magnus-0.5 (ruby=3.2, os=macos-latest)	3m 13s
magnus-0.5 (ruby=ruby-head, os=macos-latest)	3m 29s
magnus-head (ruby=2.7, os=ubuntu-latest)	4m 52s
magnus-head (ruby=3.2, os=ubuntu-latest)	3m 59s
magnus-head (ruby=ruby-head, os=ubuntu-latest)	3m 33s
magnus-head (ruby=2.7, os=windows-latest)	10m 5s
magnus-head (ruby=3.2, os=windows-latest)	12m 23s
magnus-head (ruby=2.7, os=macos-latest)	4m 37s
magnus-head (ruby=3.2, os=macos-latest)	4m 2s
magnus-head (ruby=ruby-head, os=macos-latest)	4m 12s
	1h 59m 55s

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