Update soy docs to use map.keys() instead of deprecated mapKeys(map)
Update soy docs to use map.keys() instead of deprecated mapKeys(map)

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=357212722

google/closure-templates,google/closure-templates,google/closure-templates,google/closure-templates,google/closure-templates