Change header to be polkadot (#46)

Author: TarikGul

frontend/src/App.tsx

@@ -67,7 +67,7 @@ function App() {
       <header>
         <div className="logo">
           <img src={polkadotLogo} alt="Polkadot Logo" />
-          <h1>Asset Hub Kusama Migration Monitor</h1>
+          <h1>Asset Hub Polkadot Migration Monitor</h1>
         </div>
         <div className="header-info">
           {process.env.ALLOW_REMOTE_BACKEND === 'true' && (