Update note on action description requirement

Clarified that the description is not required for composite actions.

As a proof of concept, I deleted my 'description' key from my composite action and called it, with everything still working.

Author: mcummings128

content/actions/reference/workflows-and-actions/metadata-syntax.md

@@ -34,7 +34,7 @@ category:
 ## `description`
 
 **Required** A short description of the action.
-
+Note: This is not required for composite actions.
 ## `inputs`
 
 **Optional** Input parameters allow you to specify data that the action expects to use during runtime. {% data variables.product.prodname_dotcom %} stores input parameters as environment variables. We recommend using lowercase input ids.