docs(website): remove Slack and GitHub links from Community section (#4051)

Author: wsxiaoys

website/docusaurus.config.js

@@ -122,19 +122,6 @@ export default {
               },
             ],
           },
-          {
-            title: 'Community',
-            items: [
-              {
-                label: 'Slack',
-                href: 'https://slack.tabbyml.com',
-              },
-              {
-                label: 'GitHub',
-                href: 'https://github.com/TabbyML/tabby',
-              },
-            ],
-          },
           {
             title: 'More',
             items: [