Remove support for Python 3.8 from dm_control.

Python 3.8 has been deprecated upstream, and any tests depending on Homebrew already stopped working. Following our support policy, we are removing support for 3.8 from our packages, too.

PiperOrigin-RevId: 686036245
Change-Id: I2f7433aac26f9c9fe3c9a2f1f57d88e67857fc9c

requirements.txt

@@ -9,14 +9,12 @@ mock==5.1.0
 mujoco==3.2.3
 nose==1.3.7
 nose-xunitmp==0.4.1
-numpy==1.24.4; python_version == '3.8'
 numpy==1.26.4; python_version >= '3.9'
 Pillow==10.3.0
 protobuf==3.19.4  # TensorFlow requires protobuf<3.20 (b/182876485)
 pyopengl==3.1.7
 pyparsing==3.1.2
 requests==2.32.3
-scipy==1.10.1; python_version == '3.8'
 scipy==1.13.1; python_version >= '3.9'
 setuptools==70.0.0
 tqdm==4.66.4

setup.py

@@ -197,7 +197,7 @@ def is_excluded(s):
         'License :: OSI Approved :: Apache Software License',
     ],
     keywords='machine learning control physics MuJoCo AI',
-    python_requires='>=3.8',
+    python_requires='>=3.9',
     install_requires=[
         'absl-py>=0.7.0',
         'dm-env',