Database
[{"contracts":["5a934e000102030405000000","5a934e000102030405000001","5a934e000102030405000002"],"_id":"613bd938774f3b0fa8f9c1ce","address":"1"},{"contracts":["5a934e000102030405000000","5a934e000102030405000001","5a934e000102030405000002"],"_id":"613bd938774f3b0fa8f9c1cf","address":"2"}]
Query
db.collection.update({"_id":"613bd938774f3b0fa8f9c1ce"},{"$pull":{"contracts":"5a934e000102030405000000"}})