MM-23747 fix Sprintf linter errors (#14196)

- replace all instances of `fmt.Sprintf("whatever")` with simply "whatever".

- replace all instances of `fmt.Println(fmt.Sprintf("whatever %d", i))` with `fmt.Printf("whatever %d\n", i)`

app/channel_test.go

@@ -811,8 +811,8 @@ func TestGetChannelMembersTimezones(t *testing.T) {
 func TestGetChannelsForUser(t *testing.T) {
 	th := Setup(t).InitBasic()
 	channel := &model.Channel{
-		DisplayName: fmt.Sprintf("Public"),
-		Name:        fmt.Sprintf("public"),
+		DisplayName: "Public",
+		Name:        "public",
 		Type:        model.CHANNEL_OPEN,
 		CreatorId:   th.BasicUser.Id,
 		TeamId:      th.BasicTeam.Id,