fix: typo in description of an input for action.yaml (#452)

Author: yutatokoi

action.yaml

@@ -8,7 +8,7 @@ inputs:
     required: false
     default: 'image'
   image-ref:
-    description: 'image reference(for backward compatibility)'
+    description: 'image reference (for backward compatibility)'
     required: false
   input:
     description: 'reference of tar file to scan'