[stubsabot] Bump braintree to 4.18.* (#9502)

Release: https://pypi.org/pypi/braintree/4.18.0
Homepage: https://developer.paypal.com/braintree/docs/reference/overview

Author: github-actions[bot]

stubs/braintree/METADATA.toml

@@ -1 +1 @@
-version = "4.17.*"
+version = "4.18.*"