chore(workflows): Use ubuntu-latest #1388

Job	Run time
test / test-dart-vm (3.0.1)	2m 12s
test / test-dart-vm (stable)	2m 32s
native_test / test-dart-native (macos-latest)	2m 2s
native_test / test-dart-native (windows-latest)	5m 12s
ddc_test / test-dart-ddc (3.0.1, chrome)	3m 42s
ddc_test / test-dart-ddc (3.0.1, firefox)	2m 59s
ddc_test / test-dart-ddc (stable, chrome)	3m 31s
ddc_test / test-dart-ddc (stable, firefox)	3m 15s
dart2js_test / test-dart-2js (3.0.1, chrome)	4m 13s
dart2js_test / test-dart-2js (3.0.1, firefox)	3m 15s
dart2js_test / test-dart-2js (stable, chrome)	3m 26s
dart2js_test / test-dart-2js (stable, firefox)	3m 51s
	40m 10s

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