Update konstantinos.md

Author: pliang279

src/content/people/konstantinos.md

@@ -1,6 +1,6 @@
 ---
 name: "Konstantinos Kontras"
 title: "Visiting researcher"
-avatar: "https://kkontras.github.io/authors/admin/prof_pic.jpg"
+avatar: "./images/konstantinos.png"
 website: "https://kkontras.github.io/"
 ---