PLT-6217 Fixes system message posted to Town Square when a member leaves a team (#7752)

* Fixes system message posted to Town Square when adding/removing team member (#6483)

Fixes unit test method call to match RemoveUserFromTeam modification (#6483)

Fixes system message posted to Town Square when adding/removing team member (#6483)

Removes unnessary error message

* Updates system message when a user leaves a team (#6483)

* Changes system message when a user is removed from team (#6483)

* Adds a new string to be post to town-square when a member is added to a team (#6483)

cmd/platform/team.go

@@ -130,7 +130,7 @@ func removeUserFromTeam(a *app.App, team *model.Team, user *model.User, userArg
 		CommandPrintErrorln("Can't find user '" + userArg + "'")
 		return
 	}
-	if err := a.LeaveTeam(team, user); err != nil {
+	if err := a.LeaveTeam(team, user, ""); err != nil {
 		CommandPrintErrorln("Unable to remove '" + userArg + "' from " + team.Name + ". Error: " + err.Error())
 	}
 }