Remove duplicate plugin tests (#126582)

Removes two plugin tests that aren't actually doing anything useful.

When they were added they were testing v2-embedding plugins in a v1-embedding app, but support for creating v1-embedding apps--and the environment variable that these tests were using to, in theory, trigger them--was removed several years ago in #61203. That means that these tests are in practice exact duplicates of the copies just above without the ennvironment variables.

Fixes https://github.com/flutter/flutter/issues/122200

dev/devicelab/bin/tasks/plugin_test.dart

@@ -9,13 +9,6 @@ Future<void> main() async {
   await task(combine(<TaskFunction>[
     PluginTest('apk', <String>['-a', 'java', '--platforms=android']).call,
     PluginTest('apk', <String>['-a', 'kotlin', '--platforms=android']).call,
-    // These create the plugins using the new v2 plugin templates but create the
-    // apps using the old v1 embedding app templates to make sure new plugins
-    // are by default backward compatible.
-    PluginTest('apk', <String>['-a', 'java', '--platforms=android'], pluginCreateEnvironment:
-        <String, String>{'ENABLE_ANDROID_EMBEDDING_V2': 'true'}).call,
-    PluginTest('apk', <String>['-a', 'kotlin', '--platforms=android'], pluginCreateEnvironment:
-        <String, String>{'ENABLE_ANDROID_EMBEDDING_V2': 'true'}).call,
     // Test that Dart-only plugins are supported.
     PluginTest('apk', <String>['--platforms=android'], dartOnlyPlugin: true).call,
     // Test that FFI plugins are supported.