Remove substack link

Everything's in the Blog now

Author: DanGould

docusaurus.config.ts

@@ -129,11 +129,6 @@ const config: Config = {
           label: "Discord",
           position: "right",
         },
-        {
-          href: "https://payjoin.substack.com/",
-          label: "News",
-          position: "right",
-        },
         {
           href: "https://github.com/payjoin",
           label: "GitHub",