Remove 'es6-impl' from the debug loader, since it's no longer used anywhere.
Remove 'es6-impl' from the debug loader, since it's no longer used anywhere.

RELNOTES: n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=238370927

lucidsoftware/closure-library,google/closure-library,google/closure-library,google/closure-library,lucidsoftware/closure-library,lucidsoftware/closure-library,lucidsoftware/closure-library,google/closure-library,google/closure-library