fix(dev-hub): address review feedback on API key copy

Restores the original placeholder wording since a Free-tier API token can
also be rate-limited, and drops the em-dash / "no rate limits" overclaim
from both hint branches.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aditya520

apps/developer-hub/src/components/Playground/AccessTokenInput/index.tsx

@@ -48,16 +48,16 @@ export function AccessTokenInput({ className }: AccessTokenInputProps) {
             onChange={(event) => {
               updateConfig({ accessToken: event.target.value });
             }}
-            placeholder="Paste your API key for unlimited streams (optional)"
+            placeholder="Leave empty to use demo token (rate limited)"
             type="password"
             value={config.accessToken}
           />
         </div>
 
         <span className={styles.hint}>
           {isUsingDemoToken
-            ? "Using a shared demo token — rate-limited for fair use. Paste your own API key for unlimited streams."
-            : "Using your API key — no rate limits. Sent only to authorize your stream; never stored."}
+            ? "Using a shared demo token is rate-limited for fair use. Paste your own API key for unlimited streams."
+            : "Using your API key. Sent only to authorize your stream and never stored."}
         </span>
       </div>
     </div>