chore: fix gpu notebook protobuf version (#1959)

deep-learning/src/main/python/horovod_installation.sh

@@ -10,6 +10,7 @@ pip install pytorch-lightning==1.5.0
 pip install torchvision==0.12.0
 pip install transformers==4.15.0
 pip install petastorm>=0.12.0
+pip install protobuf==3.20.3
 
 # Remove Outdated Signing Key:
 sudo apt-key del 7fa2af80