[MM-15194] Store: Migrate Emoji.Save to Sync as default #10642 (#10955)

* Store: Migrate Emoji.Save to Sync as default #10642

* Store: use require.Nil helper function to assert nil

app/helper_test.go

@@ -387,17 +387,17 @@ func (me *TestHelper) CreateGroup() *model.Group {
 func (me *TestHelper) CreateEmoji() *model.Emoji {
 	utils.DisableDebugLogForTest()
 
-	result := <-me.App.Srv.Store.Emoji().Save(&model.Emoji{
+	emoji, err := me.App.Srv.Store.Emoji().Save(&model.Emoji{
 		CreatorId: me.BasicUser.Id,
 		Name:      model.NewRandomString(10),
 	})
-	if result.Err != nil {
-		panic(result.Err)
+	if err != nil {
+		panic(err)
 	}
 
 	utils.EnableDebugLogForTest()
 
-	return result.Data.(*model.Emoji)
+	return emoji
 }
 
 func (me *TestHelper) AddReactionToPost(post *model.Post, user *model.User, emojiName string) *model.Reaction {