Lower protobuf version requirement.

This is to prevent conflict with TensorFlow. Fixes #339.

PiperOrigin-RevId: 472258727
Change-Id: I886360eb687d62192bad2ccb94266c207efd2050

Author: saran-t

dm_control/locomotion/mocap/mocap_pb2.py

@@ -12,7 +12,7 @@ nose-xunitmp==0.4.1
 numpy==1.21.6; python_version == '3.7'
 numpy==1.23.1; python_version >= '3.8'
 Pillow==9.2.0
-protobuf==3.20.1
+protobuf==3.19.4  # TensorFlow requires protobuf<3.20 (b/182876485)
 pyopengl==3.1.6
 pyparsing==2.4.7
 requests==2.28.1

requirements.txt

@@ -203,7 +203,7 @@ def is_excluded(s):
         'lxml',
         'mujoco >= 2.2.1',
         'numpy >= 1.9.0',
-        'protobuf >= 3.20.1',
+        'protobuf >= 3.19.4',  # TensorFlow requires protobuf<3.20 (b/182876485)
         'pyopengl >= 3.1.4',
         'pyparsing < 3.0.0',
         'requests',