Some tests of VersionFreshnessValidator are incorrect

[royarg02]

Tests for checking whether VersionFreshnessValidator.run() is pinging the server or not (see this and these tests), have a bug. The line

expect(cache.setVersionStamp, true);

which is used to check whether there has been a write to the cache, only possible when the tool tries to ping the server, actually satisfy because of these lines:

flutter/packages/flutter_tools/lib/src/version.dart

Lines 976 to 982 in ec02990

	await Future.wait<void>(<Future<void>>[
	stamp.store(
	newTimeWarningWasPrinted: now,
	cache: cache,
	),
	Future<void>.delayed(pauseTime),
	]);

VersionFreshnessValidator does not involve in pinging the server in anyway, instead it is handled by _getLatestAvailableFlutterDate.