Merge pull request #1305 from vojtatom/showcase-update-flocking-contribution-24

fix: updated image and url for challenge flocking contribution 24

Author: shiffman

content/videos/challenges/124-flocking-simulation/showcase/contribution24.json

@@ -1,6 +1,6 @@
 {
   "title": "3D flocking in C++ and compute shaders with octree and regular grid",
-  "url": "https://www.vojtatom.cz/flocking/",
+  "url": "https://vojtatom.github.io/flocking.cpp",
   "author": {
     "name": "Vojtěch Tomas",
     "url": "https://vojtatom.cz/"