Pin the version of gym installed in the RL tutorial

Versions of Gym after 0.24.1 have a compatibility problem with the code
in the `quantum_reinforcement_learning.ipynb` tutorial. Making sure to
get 0.24.1 solves that problem.

Author: mhucka

docs/tutorials/quantum_reinforcement_learning.ipynb

@@ -169,7 +169,7 @@
    },
    "outputs": [],
    "source": [
-    "!pip install gym"
+    "!pip install gym==0.24.1"
    ]
   },
   {