Update siteConfig.js (#7922)

Modifications
Sync the Pulsar project description with the latest version on home page.

site2/website/siteConfig.js

@@ -179,8 +179,8 @@ const siteConfig = {
   githubUrl: githubUrl,
 
   projectDescription: `
-    Apache Pulsar is an open-source distributed pub-sub messaging system originally
-    created at Yahoo and now part of the Apache Software Foundation
+    Apache Pulsar is a cloud-native, distributed messaging and streaming platform originally
+    created at Yahoo! and now a top-level Apache Software Foundation
   `,
 
   markdownPlugins: [