Test using mongo 4.0 (#12618)
Test using mongo 4.0 (#12618)

[IMPROVE] CircleCI to use MongoDB 4.0 for testing
4thParty/Rocket.Chat,Sing-Li/Rocket.Chat,pkgodara/Rocket.Chat,4thParty/Rocket.Chat,inoio/Rocket.Chat,subesokun/Rocket.Chat,inoio/Rocket.Chat,subesokun/Rocket.Chat,VoiSmart/Rocket.Chat,pkgodara/Rocket.Chat,inoio/Rocket.Chat,Sing-Li/Rocket.Chat,pkgodara/Rocket.Chat,4thParty/Rocket.Chat,subesokun/Rocket.Chat,subesokun/Rocket.Chat,pkgodara/Rocket.Chat,Sing-Li/Rocket.Chat,Sing-Li/Rocket.Chat,VoiSmart/Rocket.Chat,4thParty/Rocket.Chat,VoiSmart/Rocket.Chat