feat: Disable deprecated chain option in X402LeftSection

Co-authored-by: yashjoisar <[email protected]>

Author: cursoragent

apps/playground-web/src/app/x402/components/X402LeftSection.tsx

@@ -128,6 +128,7 @@ export function X402LeftSection(props: {
               onChange={handleChainChange}
               placeholder="Select a chain"
               className="bg-card"
+              disableDeprecated
             />
           </div>