chore: Update social media links

nginx.d/social.conf

@@ -3,7 +3,7 @@ server {
         server_name social.codimd.org social.hedgedoc.org;
 
         location /mastodon {
-            return 302 https://social.snopyta.org/@HedgeDoc;
+            return 302 https://fosstodon.org/@HedgeDoc;
         }
 
         location /twitter {
@@ -11,6 +11,6 @@ server {
         }
 
         location / {
-            return 302 https://social.snopyta.org/@HedgeDoc;
+            return 302 https://fosstodon.org/@HedgeDoc;
         }
 }