Disable flaky LineMetrics test (#49364)

packages/flutter/test/painting/text_painter_test.dart

@@ -801,5 +801,10 @@ void main() {
     expect(lines[1].lineNumber, 1);
     expect(lines[2].lineNumber, 2);
     expect(lines[3].lineNumber, 3);
-  }, skip: !isLinux);
+
+  // Disable this test, this is causing a large amount of flaking and
+  // does not have a clear cause. This may or may not be a dart compiler
+  // issue or similar. See https://github.com/flutter/flutter/issues/43763
+  // for more info.
+  }, skip: true);
 }