Update ppo documentation (remove redundant and) (#874)

* Update ppo documentation (remove redundant and)

PTAL, thanks!

* Update changelog

* Pin ale-py version

Co-authored-by: Antonin Raffin <antonin.raffin@dlr.de>

docs/misc/changelog.rst

@@ -35,6 +35,7 @@ Others:
 Documentation:
 ^^^^^^^^^^^^^^
 - Added link to gym doc and gym env checker
+- Fix typo in PPO doc (@bcollazo)
 
 
 Release 1.5.0 (2022-03-25)
@@ -964,4 +965,4 @@ And all the contributors:
 @wkirgsn @AechPro @CUN-bjy @batu @IljaAvadiev @timokau @kachayev @cleversonahum
 @eleurent @ac-93 @cove9988 @theDebugger811 @hsuehch @Demetrio92 @thomasgubler @IperGiove @ScheiklP
 @simoninithomas @armandpl @manuel-delverme @Gautam-J @gianlucadecola @buoyancy99 @caburu @xy9485
-@Gregwar @ycheng517 @quantitative-technologies
+@Gregwar @ycheng517 @quantitative-technologies @bcollazo

setup.py

@@ -116,7 +116,7 @@ setup(
             # For render
             "opencv-python",
             # For atari games,
-            "ale-py~=0.7.4",
+            "ale-py==0.7.4",
             "autorom[accept-rom-license]~=0.4.2",
             "pillow",
             # Tensorboard support

stable_baselines3/ppo/ppo.py

@@ -19,7 +19,7 @@ class PPO(OnPolicyAlgorithm):
     Paper: https://arxiv.org/abs/1707.06347
     Code: This implementation borrows code from OpenAI Spinning Up (https://github.com/openai/spinningup/)
     https://github.com/ikostrikov/pytorch-a2c-ppo-acktr-gail and
-    and Stable Baselines (PPO2 from https://github.com/hill-a/stable-baselines)
+    Stable Baselines (PPO2 from https://github.com/hill-a/stable-baselines)
 
     Introduction to PPO: https://spinningup.openai.com/en/latest/algorithms/ppo.html