build: update license identifiers in pyproject.toml (#1249)

Author: jackwotherspoon

pyproject.toml

@@ -20,7 +20,8 @@ build-backend = "setuptools.build_meta"
 description = "Google Cloud SQL Python Connector library"
 name = "cloud-sql-python-connector"
 authors = [{ name = "Google LLC", email = "[email protected]" }]
-license = { text = "Apache 2.0" }
+license = "Apache-2.0"
+license-files = ["LICENSE"]
 requires-python = ">=3.9"
 readme = "README.md"
 classifiers = [
@@ -30,7 +31,6 @@ classifiers = [
     # "Development Status :: 5 - Production/Stable"
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: Apache Software License",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.9",