chore: disable white paper download banner (#1556)

Author: GuangmingLuo

content/zh/_index.html

@@ -1,7 +1,7 @@
 +++
 title = "CloudWeGo"
 linkTitle = "CloudWeGo"
-show_banner = true
+show_banner = false
 +++
 
 {{< blocks/cover title="欢迎使用 CloudWeGo" subtitle="构建企业级云原生中间件的领先实践！" image_anchor="top" height="full" color="dark" >}}