chore(workflows): Use ubuntu-latest #1512

Job	Run time
test / test-dart-vm (3.0.1)	1m 37s
test / test-dart-vm (stable)	2m 13s
ddc_test / test-dart-ddc (3.0.1, chrome)	3m 35s
native_test / test-dart-native (macos-latest)	3m 38s
ddc_test / test-dart-ddc (3.0.1, firefox)	3m 51s
native_test / test-dart-native (windows-latest)	3m 36s
ddc_test / test-dart-ddc (stable, chrome)	3m 43s
ddc_test / test-dart-ddc (stable, firefox)	4m 15s
dart2js_test / test-dart-2js (3.0.1, chrome)	5m 3s
dart2js_test / test-dart-2js (3.0.1, firefox)	4m 33s
dart2js_test / test-dart-2js (stable, chrome)	3m 54s
dart2js_test / test-dart-2js (stable, firefox)	4m 46s
	44m 44s

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