Revert "Fix Platform.script for flutter_tester"

This reverts commit b14d346.

With #46911, the Platform.script API
will return a URI for the compiled temporary wrapper script generated by
"flutter test".  This will cause issues for tests that expect Platform.script
to reflect the directory where "flutter test" was launched.

shell/testing/tester_main.cc

@@ -526,7 +526,6 @@ int main(int argc, char* argv[]) {
     // it as a positional argument instead.
     settings.application_kernel_asset = command_line.positional_args()[0];
   }
-  settings.advisory_script_uri = settings.application_kernel_asset;
 
   if (settings.application_kernel_asset.empty()) {
     FML_LOG(ERROR) << "Dart kernel file not specified.";

testing/dart/BUILD.gn

@@ -38,7 +38,6 @@ tests = [
   "paragraph_test.dart",
   "path_test.dart",
   "picture_test.dart",
-  "platform_test.dart",
   "platform_view_test.dart",
   "plugin_utilities_test.dart",
   "semantics_test.dart",