chore: version bump built_value and built_value_generator #1853

Job	Run time
test / test-dart-vm (3.0.1)	3m 5s
test / test-dart-vm (stable)	2m 21s
native_test / test-dart-native (macos-latest)	4m 14s
native_test / test-dart-native (windows-latest)	3m 15s
ddc_test / test-dart-ddc (3.0.1, chrome)	3m 11s
ddc_test / test-dart-ddc (3.0.1, firefox)	3m 22s
ddc_test / test-dart-ddc (stable, chrome)	3m 13s
ddc_test / test-dart-ddc (stable, firefox)	3m 18s
dart2js_test / test-dart-2js (3.0.1, chrome)	3m 34s
dart2js_test / test-dart-2js (3.0.1, firefox)	3m 37s
dart2js_test / test-dart-2js (stable, chrome)	3m 23s
dart2js_test / test-dart-2js (stable, firefox)	3m 33s
	40m 6s

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