Fixed x link

Author: kabutz

app/data/authors.yaml

@@ -41,7 +41,7 @@
   email: heinz@javaspecialists.eu
   photo_url: https://javaspecialists.eu/pics/gb/heinz2-300x300.jpg
   github: kabutz
-  twitter: kabutz
+  twitter: heinzkabutz
   website: https://www.javaspecialists.eu
   description: |
     Heinz is the author of <a href="https://www.javaspecialists.eu">The Java Specialists' Newsletter</a>,