remove old-nng tile

client/src/components/landing_page.tsx

@@ -141,16 +141,6 @@ Dieses Spiel führt die Grundlagen zur Beweisführung in Lean ein und schneidet
         image={coverRobo}
         language="German"
         />
-
-      <GameTile
-        title="NNG (OLD)"
-        gameId="g/hhu-adam/nng4-old"
-        intro="The old version of the NNG copied from lean3."
-        description="This version is not maintained and might break at any point. You should play the new version instead"
-        worlds="9"
-        levels="72"
-        language="English"
-        />
     </div>
     <section>
       <div className="wrapper">