removing markus 2048 gym import since it produces errors now

conda installation no longer works with his import but this is only necessary for running the 2048 solution notebook which is already provided in an executed state such that students can see everything

environment.yml

@@ -18,5 +18,5 @@ dependencies:
   - altair
   - opentsne
   - gym
-  - pip:
-    - git+https://github.com/dvmarkusvogl/gym-2048.git
+#  - pip:
+#    - git+https://github.com/dvmarkusvogl/gym-2048.git