chore(workflows): Use ubuntu-latest #1083

Job	Run time
test / test-dart-vm (3.0.1)	1m 39s
test / test-dart-vm (stable)	1m 49s
native_test / test-dart-native (macos-latest)	2m 37s
native_test / test-dart-native (windows-latest)	6m 12s
dart2js_test / test-dart-2js (3.0.1, chrome)	10m 50s
dart2js_test / test-dart-2js (3.0.1, firefox)	11m 15s
dart2js_test / test-dart-2js (stable, chrome)	9m 44s
ddc_test / test-dart-ddc (3.0.1, chrome)	7m 16s
dart2js_test / test-dart-2js (stable, firefox)	10m 5s
ddc_test / test-dart-ddc (3.0.1, firefox)	7m 20s
ddc_test / test-dart-ddc (stable, chrome)	6m 50s
ddc_test / test-dart-ddc (stable, firefox)	6m 41s
	1h 22m 18s

Provide feedback