Add missing test case for lf.structs.MapSet#delete. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=107640367
Add missing test case for lf.structs.MapSet#delete.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=107640367

ralic/lovefield,ralic/lovefield,google/lovefield,ralic/lovefield,google/lovefield,google/lovefield