overlay profiles: Add accept keywords for dev-python/cython

Author: krnowak

sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.accept_keywords

@@ -97,6 +97,7 @@ dev-cpp/azure-security-keyvault-keys
 # Keep versions on both arches in sync.
 =dev-libs/raft-0.22.1 ~arm64
 =dev-python/cryptography-45.0.4 ~arm64
+=dev-python/cython-3.1.2 ~arm64
 =dev-python/msgpack-1.1.1 ~arm64
 
 # No arm64 keyword in package.