Move apollo-demo, scripts/docker-quick-start and scripts/apollo-on-kubernetes out of main repository (#4440)

* move apollo-demo to https://github.com/apolloconfig/apollo-demo-java
* move scripts/docker-quick-start to https://github.com/apolloconfig/apollo-quick-start
* move scripts/apollo-on-kubernetes to https://github.com/apolloconfig/apollo-on-kubernetes

Author: nobodyiam

CHANGES.md

@@ -15,6 +15,7 @@ Apollo 2.1.0
 * [Optimize Spring-Security Firewall Deny Request Response 400](https://github.com/apolloconfig/apollo/pull/4428)
 * [Optimize the UI experience of open platform authorization management](https://github.com/apolloconfig/apollo/pull/4436)
 * [Allow users to associate multiple public namespaces at a time](https://github.com/apolloconfig/apollo/pull/4437)
+* [Move apollo-demo, scripts/docker-quick-start and scripts/apollo-on-kubernetes out of main repository](https://github.com/apolloconfig/apollo/pull/4440)
 
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 All issues and pull requests are [here](https://github.com/apolloconfig/apollo/milestone/11?closed=1)