Remove duplicate type (#19593)
Remove duplicate type (#19593)

* Remove duplicate type

* Remove extraneouse es2015 sources from gulpfile

* Revert 6f1cdf3

basarat/TypeScript,minestarks/TypeScript,kitsonk/TypeScript,nojvek/TypeScript,minestarks/TypeScript,nojvek/TypeScript,donaldpipowitch/TypeScript,TukekeSoft/TypeScript,weswigham/TypeScript,RyanCavanaugh/TypeScript,kitsonk/TypeScript,kpreisser/TypeScript,microsoft/TypeScript,RyanCavanaugh/TypeScript,alexeagle/TypeScript,weswigham/TypeScript,SaschaNaz/TypeScript,donaldpipowitch/TypeScript,kpreisser/TypeScript,SaschaNaz/TypeScript,nojvek/TypeScript,basarat/TypeScript,Microsoft/TypeScript,alexeagle/TypeScript,basarat/TypeScript,SaschaNaz/TypeScript,microsoft/TypeScript,Microsoft/TypeScript,RyanCavanaugh/TypeScript,nojvek/TypeScript,kpreisser/TypeScript,TukekeSoft/TypeScript,minestarks/TypeScript,donaldpipowitch/TypeScript,alexeagle/TypeScript,weswigham/TypeScript,Microsoft/TypeScript,donaldpipowitch/TypeScript,kitsonk/TypeScript,microsoft/TypeScript,basarat/TypeScript,TukekeSoft/TypeScript,SaschaNaz/TypeScript