Run go mod tidy

Author: sharadregoti

gateway/go.mod

@@ -62,7 +62,6 @@ require (
 	github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2 // indirect
 	go.etcd.io/bbolt v1.3.3
 	go.mongodb.org/mongo-driver v1.1.1
-	go.uber.org/zap v1.15.0 // indirect
 	golang.org/x/crypto v0.0.0-20200728195943-123391ffb6de
 	golang.org/x/net v0.0.0-20200707034311-ab3426394381
 	google.golang.org/api v0.18.0