Add step to release process to update CCS spec info.

Author: nickygerritsen

new_release_howto.md

@@ -4,6 +4,8 @@ on the account `domjudge@vm-domjudge`):
 
  1. Test everything. (duh...)
  1. Commit the correct version number in the `ChangeLog` and `README` files.
+ 1. Change the constants `webapp/src/Controller/API/GeneralInfoController.php`
+    to point to the correct CCS API version.
  1. `export TAG=x.y.z`
  1. Create a release version `$TAG` in Git with `$TAG` the version number
     x.y.z: