Fix invalid SPDX license expression in setup.cfg metadata

Author: TheFunctionalGuy

setup.cfg

@@ -7,7 +7,7 @@ long_description_content_type = text/x-rst
 url = https://uritemplate.readthedocs.org
 author = Ian Stapleton Cordasco
 author_email = [email protected]
-license = BSD 3-Clause OR Apache-2.0
+license = BSD-3-Clause OR Apache-2.0
 license_files = LICENSE
 classifiers =
     Development Status :: 5 - Production/Stable