Update python version in setup.py and remove traces of py37 in README.md.

PiperOrigin-RevId: 518922897

Author: rtg0795

setup.py

@@ -74,7 +74,7 @@ def select_constraint(default, nightly=None, git_master=None):
     package_data={
         'fairness_indicators': ['documentation/*'],
     },
-    python_requires='>=3.7,<3.10',
+    python_requires='>=3.8,<3.10',
     install_requires=REQUIRED_PACKAGES,
     tests_require=REQUIRED_PACKAGES,
     # PyPI package information.

tensorboard_plugin/setup.py

@@ -79,7 +79,7 @@ def select_constraint(default, nightly=None, git_master=None):
             'fairness_indicators = tensorboard_plugin_fairness_indicators.plugin:FairnessIndicatorsPlugin',
         ],
     },
-    python_requires='>=3.7,<3.10',
+    python_requires='>=3.8,<3.10',
     install_requires=REQUIRED_PACKAGES,
     tests_require=REQUIRED_PACKAGES,
     classifiers=[
@@ -90,7 +90,6 @@ def select_constraint(default, nightly=None, git_master=None):
         'License :: OSI Approved :: Apache Software License',
         'Operating System :: OS Independent',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3 :: Only',