refactor: use kwargs for EncryptionConfig conversion

Author: larkee

google/cloud/spanner_v1/database.py

@@ -141,9 +141,7 @@ def __init__(
         self._logger = logger
 
         if type(encryption_config) == dict:
-            self._encryption_config = EncryptionConfig(
-                kms_key_name=encryption_config["kms_key_name"]
-            )
+            self._encryption_config = EncryptionConfig(**encryption_config)
         else:
             self._encryption_config = encryption_config