fix: secret example put instead of putting - permission (#683)

Author: davemooreuws

docs/secrets.mdx

@@ -125,7 +125,7 @@ latestVersion.version
 from nitric.resources import secret
 from nitric.application import Nitric
 
-api_key = secret("api-key").allow("putting")
+api_key = secret("api-key").allow("put")
 
 latest = await api_key.put("a new secret value")