Upgrading go.tools.mod (#15081)

* Upgrading to the last mattermost-utilities/mmgotool

* Remove unneeded file

* Fixing mmgotools usage

go.tools.mod

@@ -4,7 +4,7 @@ go 1.14
 
 require (
 	github.com/jstemmer/go-junit-report v0.9.1 // indirect
-	github.com/mattermost/mattermost-utilities v0.0.0-20200521071950-1be063e1b2fe // indirect
+	github.com/mattermost/mattermost-utilities/mmgotool v0.0.0-20200720080147-779d19605c57 // indirect
 	github.com/reflog/struct2interface v0.6.1 // indirect
 	github.com/vektra/mockery v1.1.2 // indirect
 )