Eliminate iOS log blacklist (#11981)

This was introduced to suppress libMobileGestalt noise originating from
libsystem_asl.dylib. Commit 39680ebf
suppresses all application log messages not originating from the
app/engine iteself on iOS 10 and above. Since the log message in
question is only emitted on devices running iOS >= 10.3.0, this
blacklist no longer necessary.

packages/flutter_tools/lib/src/ios/devices.dart

@@ -385,19 +385,12 @@ class _IOSDeviceLogReader extends DeviceLogReader {
   }
 
   void _onLine(String line) {
-    // Lines starting with these strings are suppressed from output as noise.
-    const List<String> blacklist = const <String>[
-      'libMobileGestalt ',
-    ];
-
     final Match match = _lineRegex.firstMatch(line);
 
     if (match != null) {
       final String logLine = line.substring(match.end);
-      if (!blacklist.any(logLine.startsWith)) {
-        // Only display the log line after the initial device and executable information.
-        _linesController.add(logLine);
-      }
+      // Only display the log line after the initial device and executable information.
+      _linesController.add(logLine);
     }
   }
 

packages/flutter_tools/test/ios/devices_test.dart

@@ -79,7 +79,7 @@ f577a7903cc54959be2e34bc4f7f80b7009efcf4
       mockIMobileDevice = new MockIMobileDevice();
     });
 
-    testUsingContext('suppresses blacklisted lines from output', () async {
+    testUsingContext('suppresses non-Flutter lines from output', () async {
       when(mockIMobileDevice.startLogger()).thenAnswer((_) {
         final Process mockProcess = new MockProcess();
         when(mockProcess.stdout).thenReturn(new Stream<List<int>>.fromIterable(<List<int>>['''