chore(workflows): Use ubuntu-latest #1514

Job	Run time
test / test-dart-vm (3.0.1)	2m 7s
test / test-dart-vm (stable)	1m 38s
dart2js_test / test-dart-2js (3.0.1, chrome)	6m 54s
ddc_test / test-dart-ddc (3.0.1, chrome)	5m 6s
dart2js_test / test-dart-2js (3.0.1, firefox)	6m 42s
native_test / test-dart-native (macos-latest)	2m 52s
ddc_test / test-dart-ddc (3.0.1, firefox)	4m 45s
dart2js_test / test-dart-2js (stable, chrome)	6m 16s
native_test / test-dart-native (windows-latest)	4m 15s
ddc_test / test-dart-ddc (stable, chrome)	4m 42s
dart2js_test / test-dart-2js (stable, firefox)	6m 7s
ddc_test / test-dart-ddc (stable, firefox)	4m 59s
	56m 23s

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