Update links to PettingZoo homepage (Unity-Technologies#6065)

This new website was introduced in the docs for PettingZoo 1.21.0 in 2022: https://pypi.org/project/pettingzoo/1.21.0/
(compare to https://pypi.org/project/pettingzoo/1.20.1/ )

Author: alex-mccarthy-unity

docs/Python-PettingZoo-API.md

@@ -1,7 +1,7 @@
 # Unity ML-Agents PettingZoo Wrapper
 
 With the increasing interest in multi-agent training with a gym-like API, we provide a
-PettingZoo Wrapper around the [Petting Zoo API](https://www.pettingzoo.ml/). Our wrapper
+PettingZoo Wrapper around the [Petting Zoo API](https://pettingzoo.farama.org/). Our wrapper
 provides interfaces on top of our `UnityEnvironment` class, which is the default way of
 interfacing with a Unity environment via Python.
 
@@ -20,7 +20,7 @@ which is a multi-agents environment with multiple different behavior names.
 ## API interface
 
 This wrapper is compatible with PettingZoo API. Please check out
-[PettingZoo API page](https://www.pettingzoo.ml/api) for more details.
+[PettingZoo API page](https://pettingzoo.farama.org/api/aec/) for more details.
 Here's an example of interacting with wrapped environment:
 
 ```python
@@ -37,8 +37,8 @@ for agent in env.agent_iter():
 ```
 
 ## Notes
-- There is support for both [AEC](https://www.pettingzoo.ml/api#interacting-with-environments)
-  and [Parallel](https://www.pettingzoo.ml/api#parallel-api) PettingZoo APIs.
+- There is support for both [AEC](https://pettingzoo.farama.org/api/aec/)
+  and [Parallel](https://pettingzoo.farama.org/api/parallel/) PettingZoo APIs.
 - The AEC wrapper is compatible with PettingZoo (PZ) API interface but works in a slightly
   different way under the hood. For the AEC API, Instead of stepping the environment in every `env.step(action)`,
   the PZ wrapper will store the action, and will only perform environment stepping when all the

ml-agents-envs/colabs/Colab_PettingZoo.ipynb

@@ -192,7 +192,7 @@
    "source": [
     "### Stepping the environment\n",
     "\n",
-    "Example of interacting with the environment in basic RL loop. It follows the same interface as described in [PettingZoo API page](https://www.pettingzoo.ml/api)."
+    "Example of interacting with the environment in basic RL loop. It follows the same interface as described in [PettingZoo API page](https://pettingzoo.farama.org/api/aec/)."
    ]
   },
   {
@@ -223,7 +223,7 @@
    "source": [
     "### Additional Environment API\n",
     "\n",
-    "All the API described in the `Additional Environment API` section in the [PettingZoo API page](https://www.pettingzoo.ml/api) are all supported. A few examples are shown below."
+    "All the API described in the `Additional Environment API` section in the [PettingZoo API page](https://pettingzoo.farama.org/api/aec/) are all supported. A few examples are shown below."
    ]
   },
   {