Declare Python 3.9+ envs supported

This is necessary for the CI to match the expected dists.
Additionally, the metadata makes the dependency resolver aware of
the supported runtimes.

pyproject.toml

@@ -27,11 +27,14 @@ upstreaming = [
 name = 'pre-commit-terraform'
 classifiers = [
   'License :: OSI Approved :: MIT License',
-  'Programming Language :: Python :: 2',
-  'Programming Language :: Python :: 2.7',
+
   'Programming Language :: Python :: 3',
-  'Programming Language :: Python :: 3.6',
-  'Programming Language :: Python :: 3.7',
+  'Programming Language :: Python :: 3.9',
+  'Programming Language :: Python :: 3.10',
+  'Programming Language :: Python :: 3.11',
+  'Programming Language :: Python :: 3.12',
+  'Programming Language :: Python :: 3.13',
+
   'Programming Language :: Python :: Implementation :: CPython',
   'Programming Language :: Python :: Implementation :: PyPy',
 ]
@@ -41,6 +44,7 @@ dynamic = [
   'urls',
   'version',
 ]
+python-version = ">= 3.9"
 
 [[project.authors]]
 name = 'Anton Babenko'