Remove unused variables / code (#7736)

* remove unused variables / code

* fix bug in testPostStoreGetOldest

api/context.go

@@ -32,7 +32,6 @@ type Context struct {
 	T             goi18n.TranslateFunc
 	Locale        string
 	TeamId        string
-	isSystemAdmin bool
 }
 
 func (api *API) ApiAppHandler(h func(*Context, http.ResponseWriter, *http.Request)) http.Handler {

api/emoji.go

@@ -192,10 +192,6 @@ func getEmojiImage(c *Context, w http.ResponseWriter, r *http.Request) {
 	w.Write(image)
 }
 
-func getEmojiImagePath(id string) string {
-	return "emoji/" + id + "/image"
-}
-
 func resizeEmoji(img image.Image, width int, height int) image.Image {
 	emojiWidth := float64(width)
 	emojiHeight := float64(height)