chore: updates minimum python runtime and trove classifier

Author: chalmerlowe

packages/bigframes/setup.py

@@ -140,6 +140,7 @@
         "License :: OSI Approved :: Apache Software License",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",
@@ -156,7 +157,7 @@
         "bigframes_vendored": "third_party/bigframes_vendored",
     },
     packages=packages,
-    python_requires=">=3.10",
+    python_requires=">=3.9",
     include_package_data=True,
     zip_safe=False,
 )