Update Mastodon, remove deleted Twitter account

Author: sethmlarson

content/authors/Seth Larson.json

@@ -3,9 +3,9 @@
   "bio": "Security Developer-in-Residence at the Python Software Foundation",
   "github": "sethmlarson",
   "avatar": "",
-  "twitter": "sethmlarson",
+  "twitter": "",
   "bluesky": "sethmlarson.dev",
-  "mastodon": "https://fosstodon.org/@sethmlarson",
+  "mastodon": "https://mastodon.social/@sethmlarson",
   "website": "https://sethmlarson.dev",
   "featured": false
 }