Remove testing/lang_utils.dart, which was unused within Angular and out.
Remove testing/lang_utils.dart, which was unused within Angular and out.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128007752

matanlurey/angular,angulardart/angular,matanlurey/angular,angulardart/angular,chalin/angular2,kevmoo/angular,kevmoo/angular,kevmoo/angular,chalin/angular2,angulardart/angular,chalin/angular2,matanlurey/angular