Change android_plugin_new_output_dir_test.dart test description (#149198)

Changes the test description to what I understand it is testing. 

Context at https://discord.com/channels/608014603317936148/846507907876257822/1245077048599515157.

cc @chunfengyao as the original author, as I see you are still active on Github 🙂

packages/flutter_tools/test/integration.shard/android_plugin_new_output_dir_test.dart

@@ -25,7 +25,7 @@ void main() {
     tryToDelete(tempDir);
   });
 
-  test("error logged when plugin's build output dir was not private.", () async {
+  test('plugins use individualized build directories based on their name.', () async {
     final String flutterBin = fileSystem.path.join(
       getFlutterRoot(),
       'bin',