fix gui text error

assets/translation.json

@@ -92,6 +92,10 @@
       "en": "ID/URL",
       "zh-CN": "ID/网址"
     },
+    "gui.playlist.add.source": {
+      "en": "Source",
+      "zh-CN": "来源"
+    },
     "gui.playlist.add.prompt": {
       "en": "Please enter the ID or URL of the song you want to add.",
       "zh-CN": "输入歌单ID或者歌单网址。"

gui/playlist_list.go

@@ -55,7 +55,7 @@ func createPlaylists() fyne.CanvasObject {
 			container.NewVBox(
 				container.New(
 					layout.NewFormLayout(),
-					widget.NewLabel(i18n.T("gui.playlist.add.confirm")),
+					widget.NewLabel(i18n.T("gui.playlist.add.source")),
 					providerEntry,
 					widget.NewLabel(i18n.T("gui.playlist.add.id_url")),
 					idEntry,