Bump AiiDA core version to 2.0.4. (#312)

Co-authored-by: Jusong Yu <jusong.yeu@gmail.com>

Author: csadorf

build.json

@@ -4,7 +4,7 @@
       "default": "3.9.4"
     },
     "AIIDA_VERSION": {
-      "default": "2.0.3"
+      "default": "2.0.4"
     }
   }
 }