matrix/element/config.json: remove deprecated/removed options

Either these went away or graduated from labs as they aren't at https://github.com/matrix-org/matrix-react-sdk/blob/develop/src/settings/Settings.tsx

matrix/Element/config.json

@@ -11,27 +11,20 @@
   "features": {
 	"feature_report_to_moderators": "enable",
 	"feature_latex_maths": "enable",
-	"feature_custom_status": "enable",
-	"feature_presence_in_room_list": "enable",
+	"feature_mjolnir": "enable",
 	"feature_roomlist_preview_reactions_all": "enable",
 	"feature_roomlist_preview_reactions_dms": "enable",
 	"feature_dehydration": "enable",
 	"feature_extensible_events": "enable",
-	"feature_dnd": "enable",
-	"feature_new_layout_switcher": "enable",
-	"feature_spaces_metaspaces": "enable",
 	"feature_thread": "enable",
+	"feature_message_right_click_context_menu": "enable",
 	"feature_hidden_read_receipts": "labs",
 	"feature_custom_themes": "labs",
 	"feature_pinning": "enable",
-	"feature_custom_tags": "enable",
 	"feature_state_counters": "labs",
 	"feature_mjolnir": "labs",
-	"feature_dm_verification": "labs",
 	"feature_bridge_state": "enable",
-	"feature_presence_in_room_list": "enable",
-	"feature_ftue_notifications": "enable",
-	"feature_polls": "enable"
+	"feature_exploring_public_spaces": "enable"
   },
       "jitsi": {
         "preferredDomain": "jitsi.effi.org"