Fix typo in output decorator description

Author: denrea

articles/azure-resource-manager/bicep/diagnostics/bcp129.md

@@ -12,7 +12,7 @@ This diagnostic occurs when you specify an invalid output decorator.
 
 ## Description
 
-Function \<function-name> can't be used as a output decorator.
+Function \<function-name> can't be used as an output decorator.
 
 ## Level