docs(python): add missing await to python secret put example (#677)

Author: jyecusch

docs/secrets.mdx

@@ -127,7 +127,7 @@ from nitric.application import Nitric
 
 api_key = secret("api-key").allow("putting")
 
-latest = api_key.put("a new secret value")
+latest = await api_key.put("a new secret value")
 
 # We can get the version ID of our newly stored value
 latest.version