clarification of ExpressionTool

If in a workflow then it is the step itself, not part of a step

Author: mr-c

Workflow.yml

@@ -179,11 +179,12 @@ $graph:
   documentRoot: true
   doc: |
     An ExpressionTool is a type of Process object that can be run by itself
-    or as part of a Workflow step. It executes a pure Javascript expression
-    that has access to the same input parameters as a workflow. It is meant
-    to be used sparingly as a way to isolate complex javascript expressions
-    that need to operate on input data and produce some result. No docker
-    container is required or allowed.
+    or as a Workflow step. It executes a pure Javascript expression that has
+    access to the same input parameters as a workflow. It is meant to be used
+    sparingly as a way to isolate complex Javascript expressions that need to
+    operate on input data and produce some result; perhaps just a
+    rearrangement of the inputs. No Docker software container is required
+    or allowed.
   fields:
     - name: class
       jsonldPredicate: