chore: remove GPL code #600

Job	Run time
Test fixtures (test-ignore-tags)	3m 20s
Test fixtures (test-topo-order, --latest)	4m 16s
Test fixtures (test-date-order, --latest)	3m 23s
Test fixtures (test-topo-order-arg, --latest --topo-order)	3m 58s
Test fixtures (test-latest-with-one-tag, --latest)	3m 50s
Test fixtures (test-commit-footers)	3m 29s
Test fixtures (test-commit-preprocessors)	4m 2s
Test fixtures (test-custom-scope)	3m 35s
Test fixtures (test-limit-commits)	4m 3s
Test fixtures (test-skip-breaking-changes)	3m 24s
Test fixtures (test-split-commits)	3m 25s
Test fixtures (test-keep-a-changelog-links)	3m 33s
	44m 18s

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