Fix license SPDX code

Author: AdrianAtZyte

pyproject.toml

@@ -8,7 +8,7 @@ version = "0.2.0"
 description = "Build HTTP requests out of HTML forms"
 authors = [{name = "Zyte Group Ltd", email = "info@zyte.com"}]
 readme = "README.rst"
-license = "BSD-3-Clause"
+license = "Apache-2.0"
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Intended Audience :: Developers",