Add Content-Type header to /api/v2/key request

Replaces text/plain with application/json for proper ingestion on the backend

Author: yvaskov

ui/shared/AppError/custom/AppErrorTooManyRequests.tsx

@@ -47,6 +47,7 @@ const AppErrorTooManyRequests = ({ bypassOptions, reset }: Props) => {
         method: 'POST',
         body: JSON.stringify({ recaptcha_response: token }),
         headers: {
+          'Content-Type': 'application/json',
           'recaptcha-v2-response': token,
         },
       });