fix(js): Raise proper error if multipart upload fails (#1651)

Author: jacoblee93

js/src/client.ts

@@ -4426,6 +4426,7 @@ export class Client implements LangSmithTracingClientInterface {
         body: formData,
       }
     );
+    await raiseForStatus(response, "upload examples");
     const result = await response.json();
     return result;
   }